key: cord-022380-49oti4zg
authors: Panlilio, Adelisa L; Gerberding, Julie Louise
title: Occupational Infectious Diseases
date: 2009-05-15
journal: Textbook of Clinical Occupational and Environmental Medicine
DOI: 10.1016/b978-0-7216-8974-6.50026-9
sha: 
doc_id: 22380
cord_uid: 49oti4zg

nan

Infections acquired in the work setting represent an eclectic group that is seldom, if ever, considered together as a single category. Occupational infections involve several organ systems, respiratory, enteric, and skin infections being particularly common. Transmission involves not only casual person-to-person contact, but also a variety of other routes in special work environments. It is thus important to consider what unique features characterize the infectious diseases that can be considered occupational.

Perhaps one useful way of thinking about these diseases is that, as a group, they tend to be transmitted during work schedules or practices that are systematized. Therefore, they can be anticipated, and to the extent that unsafe infectionprone practices can be identified and modified, they can be systematically prevented. Another common feature is that many of the occupational infectious diseases can be regarded as behavioral. To the extent that unsafe practices have been defined, and practice policies modified to reduce infection risk, continued transmission often represents failure to follow accepted standards. Although certain occupational infections can be prevented by vaccines (e.g., hepatitis B), prevention often depends on simple behavioral changes, such as hand hygiene, use of gloves, and not working while ill. Finally, the anthrax cases during the fall of 2001 in the United States demonstrate the possibility of intentional (and criminal) exposure to infectious agents in the workplace, in this instance among those handling mail. 1 These intentional exposures, fortunately, are rare events, but should be considered in assessing sources of exposure for unexpected illnesses.

Prevention depends primarily on defining risky occupational practices or environments, clearly articulating policies for preventing communicable disease acquisition; removing structural barriers to compliance with policies (e.g., providing soap, hand cleansers, and gloves; allowing time away from work during periods of illness); and promoting healthy practices through behavioral change. Because infectious diseases may represent the most common cause of time lost from work, it is important for the clinician concerned with occupational medicine to understand the relationship of specific infections to specific work environments and practices, and to give at least as much attention to prevention as to diagnosis and treatment.

Occupationally acquired infections have historically been associated with animal exposures and unsanitary work environments. Modernization of agrarian techniques and improvement in sanitation have markedly decreased the incidence of these infections in the developed world, though they remain problematic in developing countries. While nearly all infectious diseases could conceivably be transmitted in the workplace, the emphasis here is on those that can be transmitted by casual contact or by specific workrelated exposures, with emphasis on diseases that are most common, most serious, or most readily prevented. Healthcare settings pose a unique challenge because of the proximity of infectious patients, susceptible patients, and healthcare personnel. Infections transmitted from personnel may have devastating effects on certain groups of patients, particularly the immunosuppressed. Likewise, certain infections transmitted to personnel, such as multidrug-resistant tuberculosis, may have serious or even fatal, consequences. Table 22 .1 summarizes the microbial etiology, sources, routes of infection, categories of workers at risk, and clinical manifestations of selected infectious diseases that have occupational predilections. A detailed discussion of waterborne microbial diseases is also provided in Chapter 54. Because the treatment of occupationally acquired infections does not differ from that of infections acquired non-occupationally, 2 the emphasis of this chapter is on the recognition and prevention of these infections. etiologic category, as well as the potential for recurrences, account for the high incidence of the common cold, even among healthy adults. Colds are more common in the fall, winter, and early spring, perhaps because of increased crowding among children during the colder seasons. Workers are most apt to acquire colds from exposure to young children in the home. Secondary cases among coworkers may then develop. Adults experience two to four colds each year, although the incidence among adult women exceeds that of men by a small margin, and smokers have a substantially increased risk.

The modes of transmission of cold viruses are not entirely elucidated. For rhinoviruses, transmission among experimental subjects occurs most readily by direct handto-hand contact, with a case followed by autoinoculation of the mucous membranes of the eye or nose. Such finger-tomucous membrane contact is ubiquitous and unavoidable. Other viruses are transmissible by aerosolized droplets. The importance of fomites (such as drinking glasses, telephone receivers, and shared office equipment) as vectors of transmission has not been determined.

Clinical manifestations Typical cold symptoms include nasal congestion, coryza, non-productive cough, sneezing, pharyngitis, and laryngeal irritation. Fever is often low grade, or may be absent. Viral upper respiratory infections usually resolve within 7-10 days, but longer durations are not uncommon.

Treatment, prevention, and control Treatment for uncomplicated infections is symptomatic. Decongestants are more useful in relieving symptoms than are antihistamines. Expectorants, saline gargles, and other nonprescription remedies are useful in some cases. Antibiotics should not be prescribed for the treatment of colds.

Colds are difficult to prevent. A policy of work restriction until symptoms improve may prevent the spread of colds but is likely to be impractical (Table 22. 2). The cost-benefit analysis of such an approach could be useful, especially in childcare and healthcare settings. Hand washing after contact with nasal secretions may be helpful. Care should be taken to use tissues when coughing or sneezing and to dispose of soiled tissues after use.

Epidemiology Influenza is a self-limited respiratory illness caused by types A and B influenza virus. Epidemics of influenza occur annually in the winter months. Adults remain susceptible to the illness despite prior episodes of infection because the antigenic structure of influenza viruses changes frequently, leading to new epidemics.

Influenza is spread from person to person, primarily by the coughing and sneezing of infected persons or sometimes by direct contact, either with infected persons or a contaminated surface. The disease is easily transmitted, and a single index case may transmit to a large number of susceptible persons in a short period of time. Adults and children typically are infectious from 1-2 days before through 5-6 days after the onset of symptoms.

Clinical syndromes An attack of influenza starts abruptly with fever, malaise, myalgia, and headache. Respiratory symptoms mimicking those of the common cold and lower respiratory symptoms including dry cough also are frequent. Fever resolves in uncomplicated cases in 48-72 hours, but other symptoms may persist for days to weeks. Influenza pneumonia, associated with hypoxemia, cough, and interstitial infiltrates, is not common in healthy adults. Elderly patients and those with underlying immunodeficiencies and chronic pulmonary diseases are at high risk for secondary bacterial pneumonias, often caused by Streptococcus pneumoniae and less often by Haemophilus influenzae and Staphylococcus aureus.

The diagnosis of influenza frequently is made on the basis of clinical symptoms and signs. However, influenza is very difficult to differentiate from respiratory illnesses caused by other pathogens on the basis of clinical symptoms alone. Other pathogens that can cause similar symptoms include, but are not limited to, Mycoplasma pneumoniae, adenovirus, respiratory syncytial virus (RSV), rhinovirus, parainfluenza viruses, and Legionella species. Many pathogens, including influenza, RSV, and parainfluenza, cause outbreaks in a seasonal pattern. Laboratory confirmatory tests can be performed to differentiate influenza from other illnesses. Appropriate patient samples to collect for laboratory testing can include a nasopharyngeal or throat swab from adults, or nasal wash or nasal aspirates, depending on which rapid test is used. Samples should be collected within the first 4 days of illness. Rapid influenza tests provide results within 24 hours; viral culture provides results in 3-10 days. Most of the rapid tests are more than 70% sensitive for detecting influenza and more than 90% specific. Because as many as 30% of samples that would be positive for influenza by viral culture may give a negative rapid test result, negative rapid tests should be followed by viral culture in a sample of the swabs collected. Viral culture can also identify other causes of influenza-like illness when influenza is not the cause.

Serum samples can be tested for influenza antibody to diagnose acute infections. Two samples should be collected per person: one sample within the first week of illness and a second sample 2-4 weeks later. If antibody levels increase from the first to the second sample, influenza infection likely occurred. Because of the length of time needed for a diagnosis of influenza by serologic testing, other diagnostic testing should be used for rapid detection of possible outbreaks. During community outbreaks, specific virologic or serologic diagnosis is not necessary once the type(s) of influenza virus causing the outbreak have been identified.

Treatment, prevention, and control Persons at high risk for serious morbidity (persons aged 65 and older, persons with chronic underlying diseases) should receive influenza vaccine annually. Immunization also is recommended for healthcare personnel and others at risk for transmitting influenza to high-risk patients ( had been associated with reduced work absenteeism and fewer deaths among nursing home patients. 3, 4 Most employers do not provide influenza prevention programs for workers outside the healthcare field. 3 Amantadine and rimantadine can reduce the duration of uncomplicated influenza A illness when administered within 2 days of onset of illness in otherwise healthy adults. Zanamavir and oseltamivir can reduce the duration of uncomplicated influenza A and B illness by approximately 1 day compared with placebo. None of these antiviral agents has been shown to be effective in preventing serious influenza-related complications. To reduce the emergence of antiviral drug-resistant viruses, the duration of therapy should typically be no longer than 5 days.

Both amantadine and rimantadine are indicated as prophylaxis for influenza A, but not for influenza B infection. Oseltamivir has been approved as prophylaxis for influenza A and B. Zanamivir has not been approved for prophylaxis, but has been shown to be as effective as oseltamivir in preventing febrile, laboratory-confirmed influenza illness. They are approximately 70-90% effective in preventing illness from influenza A. Chemoprophylaxis can be a component of influenza outbreak control programs. 3

Epidemiology The incidence of measles (rubeola) has steadily declined in the United States during the last decade and is no longer considered endemic. Measles is a major cause of morbidity and mortality worldwide. The majority of cases in the United States in recent years have been imported or secondary cases epidemiologically linked to imported cases. 5 Infected persons are highly contagious by the air-borne route during the viral prodrome, and when cough and coryza are prominent, until about 2 days after the rash appears. Infection confers lifelong immunity. Although most adults born prior to 1957 experienced childhood infection and are no longer susceptible, up to 10% may lack natural immunity. In recent epidemics, cases occurred among unimmunized children, as well as children and young adults who had received a single vaccination with live virus, and among older adults. 5 Clinical syndromes Measles progresses in several phases.

Initial virus replication occurs in the respiratory tract and leads to a primary viremic phase, which usually is asymptomatic. Release of virus from infected reticuloendothelial cells produces secondary viremia and infection of the entire respiratory system, accompanied by symptoms of coryza, cough, and in some, bronchiolitis or pneumonia. Koplik's spots, a bluish-gray enanthem most prominent on the buccal mucosa, precede development of the rash. In a typical case of measles, the rash begins on the face, then progresses to the trunk and distal extremities, and disappears in the same sequence after 5-6 days.

Treatment, prevention, and control Live-attenuated vaccine for prevention of measles became available in the early 1960s. All healthy children should receive the vaccine at age 15 months. Because 10% do not respond to a single dose of vaccine, a second dose is now recommended to improve vaccine efficacy. 7 All healthy adults born after 1957 who have not received two doses of live virus vaccine or have not experienced measles also are advised to receive vaccine (Table 22. 3). Persons who received killed vaccine have a risk of developing atypical measles, and require re-immunization with live virus vaccine. Live virus vaccine is contraindicated in infants, pregnant women, and immunosuppressed persons. Passive immunization with γ globulin is available for unimmunized persons exposed to infected individuals, but is not routinely recommended for adults. Measles rarely can exacerbate tuberculosis and cause a temporary inhibition of delayed hypersensitivity. Vaccine administration should be delayed for 1 month after tuberculin testing, and until treatment is under way in persons with active tuberculosis.

Epidemiology Mumps is a viral illness transmitted by the oral or respiratory route during contact with contaminated fomites or aerosolized droplet secretions. Mumps is less contagious than measles or rubella but produces significant morbidity, especially among adults. The incubation period ranges from 2 to 3 weeks. Virus is detectable for 6 days prior to and 9 days after the appearance of symptoms. Most adults are immune to mumps, but 10-20% of unimmunized adults have no serologic evidence of prior infection and are considered susceptible. Mumps incidence is now very low in all areas of the United States. The substantial reduction in mumps incidence during the past few years likely reflects the change in the recommendations for use of measles mumps rubella (MMR*) vaccine. 6 Clinical syndromes Parotitis typically is bilateral, but unilateral disease and involvement of other salivary glands occurs in some persons. Localized parotid tenderness and swelling, fever, and painful swallowing suggest the diagnosis. Aseptic meningitis is common but benign. Encephalitis is a rare but serious manifestation. About 25% of affected postpubescent men develop orchitis, epididymitis, or both, which is bilateral in 15% of cases and may be the sole manifestation of mumps infection. About 50% of cases of mumps orchitis result in testicular atrophy, but neither sterility nor impotence are common sequelae. Oophoritis occurs in about 5% of women with mumps.

vaccine separated by at least 1 month (i.e., a minimum of 28 days), and administered on or after the first birthday, are recommended for all children and for certain highrisk groups of adolescents and adults. 6 Adult men and healthcare personnel with no history of mumps or mumps immunization should be screened for immunity and vaccinated if they are susceptible. Immunization is contraindicated in persons with immunosuppression and in pregnant women (Table 22. 3). Passive immunization with mumps immune globulin decreases the incidence of orchitis and is recommended for mumps in adult men with a single testis. Individuals with active mumps should be excluded from work until 9 days after the onset of parotitis to avoid transmission to others in the workplace (Table 22. 2).

Epidemiology Fifth disease, also called erythema infectiosum or 'slapped cheek disease', is an infection caused by parvovirus B19. It is a common rash illness that is usually acquired in childhood, but can be an occupational risk for school and childcare personnel. It has been transmitted to personnel in healthcare settings.

Clinical syndromes Symptoms begin with mild fever and symptoms of fatigue. After a few days, the cheeks take on a flushed 'slapped' appearance. There may also be a lacy rash on the trunk, arms, and legs. Not all infected persons develop a rash. The child is usually not very ill, and the rash resolves in 7-10 days. Most persons who get fifth disease are not very ill and recover without any serious consequences. An adult who is not immune can be infected with parvovirus B19 and either have no symptoms or develop the typical rash of fifth disease, joint pain or swelling, or both. Usually, joints on both sides of the body are affected. The joints most frequently affected are the hands, wrists, and knees. The joint pain and swelling usually resolve in a week or two, but they may last several months. About 50% of adults, however, have been previously infected with parvovirus B19, have developed immunity to the virus, and cannot get fifth disease. Fifth disease is believed to be spread through direct contact, fomites, or large droplets. The period of infectivity is before the onset of the rash. Once the rash appears, a person is no longer contagious. The incubation period is 4-14 days but may be as long as 20 days.

Treatment, prevention, and control Symptomatic treatment for fever, pain, or itching is usually all that is needed for fifth disease. Adults with joint pain and swelling may need to rest, restrict their activities, and take anti-inflammatory medications to relieve symptoms. Transmission can be prevented by careful attention to hygiene, especially hand washing. No special precautions are necessary. Excluding persons with fifth disease from work, childcare centers, or schools is not likely to prevent the spread of the virus, since people are contagious before they develop the rash.

Epidemiology Pertussis, or whooping cough, is an acute infectious disease caused by the bacterium Bordetella pertussis. Pertussis continues to be an important cause of mortality in the United States. A dramatic decline in the incidence followed the widespread use of whole-cell pertussis vaccines in the mid-1940s. However, since the early 1980s, the reported pertussis incidence has increased cyclically with peaks occurring every 3-4 years. 7, 8 Contributing to this increase in incidence is the waning of immunity over time following vaccination, particularly in older age groups. Transmission most commonly occurs by contact with respiratory secretions or large aerosol droplets from the respiratory tracts of infected persons and less frequently by contact with freshly contaminated articles of an infected person. Analysis of national surveillance data for pertussis during 1997-2000 indicates that pertussis incidence continues to increase in infants too young to receive three doses of pertussis-containing vaccine and in adolescents and adults. 7 Clinical syndromes The incubation period of pertussis is commonly 7-10 days. Pertussis begins insidiously with non-specific upper respiratory symptoms including coryza, sneezing, low-grade fever, and a mild, occasional cough, similar to the common cold. The cough gradually becomes more severe, and after 1-2 weeks, the second, or paroxysmal stage, begins. Characteristically, the patient has paroxysms of numerous, rapid coughs generally with a characteristic high-pitched whoop, commonly followed by vomiting and exhaustion. The patient usually appears normal between attacks. Older persons (i.e., adolescents and adults), and those partially protected by the vaccine may become infected with B. pertussis, but usually have milder atypical disease. Pertussis in these persons may present as a more persistent cough of greater than 7 days duration, and may be indistinguishable from other upper respiratory infections. Inspiratory whoop is uncommon. B. pertussis is estimated to account for up to 7% of cough illnesses per year in older persons. Even though the disease may be milder in older persons, these infected persons may transmit the disease to other susceptible persons, including unimmunized or underimmunized infants.

The medical management of pertussis cases is primarily supportive, although antibiotics are of some value, with erythromycin being the drug of choice. This therapy eradicates the organism from secretions, thereby decreasing communicability and, if initiated early, may modify the course of the illness. There is no pertussis-containing vaccine (including DTaP) currently licensed for persons 7 years of age or older, and vaccination with DTaP currently is not recommended after the 7th birthday. Vaccine reactions are thought to be more frequent in older age groups, and pertussis-associated morbidity and mortality decrease with increasing age. Studies are currently under way to determine if a booster dose of acellular pertussis vaccine administered to older children or adults may reduce the risk of infection with B. pertussis. This may in turn reduce the risk of transmission of B. pertussis to infants and young children who may be incompletely vaccinated. Studies among older children, adolescents, and adults examining pertussis disease burden and transmission of disease to infants might guide future policy decisions on the use of acellular pertussis vaccines among persons more than seven years of age. Currently, vaccination of children more than 7 years of age, adolescents, and adults is not recommended either routinely or as an outbreak control measure. In the future, licensure of pertussis vaccines for adolescents or adults may lead to new recommendations for the use of vaccines in outbreaks. 9

Epidemiology Most epidemics of bacterial pneumonia in the workforce are due to community-acquired infections. However, legionellosis is one type of pneumonia which can be transmitted in the workplace. Legionella pneumophila is an important cause of both epidemic and endemic adult pneumonia, and it can be associated with outbreaks in the workplace. This organism colonizes aquatic ecosystems and potable water, and it is transmitted to humans by the air-borne route. Contaminated air conditioners, humidifiers, and shower heads have been implicated in outbreaks among workers and hospital patients. Outbreaks of legionellosis have occurred after persons have breathed mists that come from a water source (e.g., air conditioning cooling towers, whirlpool spas, showers) contaminated with Legionella bacteria. Persons may be exposed to these mists in homes, workplaces, hospitals, or public places. Legionellosis is not passed from person to person.

A careful occupational history should be obtained from all adults who present with pneumonia, because occupational exposures cause many otherwise rare pneumonias. Public health authorities should be notified if an occupational source is suspected so that an epidemiologic investigation to identify transmission routes and other susceptible individuals may commence.

Clinical pneumonia syndromes Community-acquired bacterial pneumonia usually is exhibited acutely, with fever, chills, productive cough, and often, pleurisy. Chest examination demonstrates signs of consolidation that may be confirmed radiologically. Sputum examination may aid implementation of empiric therapy by suggesting the etiologic pathogen. Blood cultures should be obtained when invasive disease is suspected, and lumbar puncture to evaluate meningeal fluid is indicated when symptoms or signs of meningitis are present.

Patients with legionnaire's disease usually have fever, chills, and a cough, which may be dry or productive. Some patients also have muscle aches, headache, tiredness, loss of appetite, and, occasionally, diarrhea. Chest x-rays often show pneumonia but are not pathognomonic. It is difficult to distinguish legionnaire's disease from other types of pneumonia by symptoms alone; other tests are required for diagnosis. The definitive test is culture isolation of the organism in sputum, bronchoalveolar fluid, or pleural fluid.

Other useful diagnostic tests detect the bacteria in sputum by specialized stains, identify Legionella antigens in urine samples, or compare antibody levels to Legionella in two blood samples obtained 3-6 weeks apart. The time between the patient's exposure to the bacterium and the onset of illness for legionnaire's disease is 2-10 days.

Treatment, prevention, and control Empiric ambulatory therapy of acute community-acquired bacterial pneumonia, not requiring hospitalization, should include coverage for pneumococcus and H. influenzae, if the patient has a history of chronic obstructive lung disease. Amoxicillin, trimethoprim-sulfamethoxazole and cefixime are reasonable choices, unless atypical pneumonia caused by M. pneumoniae or C. pneumoniae is suspected, in which case erythromycin is preferred. Erythromycin is the antibiotic currently recommended for treating persons with legionnaire's disease. In severe cases, a second drug, rifampin, may be added.

Preventing bacterial pneumonia is a difficult challenge. Workers at risk for pneumococcal and Haemophilus infections should be immunized, although the efficacy of this approach among patients at highest risk is debated (Table  22. 3). Influenza immunization could eliminate a major risk factor for both primary and secondary bacterial pneumonias. Occupational exposures to potential pathogens should be minimized with proper ventilation. Prevention of legionellosis is achieved by maintaining an environment that is not conducive to survival or multiplication of Legionella. The necessary preventive measures may involve water treatment or modification of air conditioning and ventilation systems. 10 These preventive steps, which may be costly, should be directed at healthcare facilities, and occupational settings where cases have been identified. 11

Epidemiology Rubella (German measles) virus is transmitted person to person by mucosal exposure to infected droplets of respiratory secretions. Since 1969, children in the United States have been routinely immunized against rubella at age 15 months, so that the majority of recognized cases today occur in adults and unimmunized children. Since 1992, reported indigenous rubella has continued to occur at a low but relatively constant endemic level with an annual average of less than 200 rubella cases. 7 Recent data indicate that the rate of rubella susceptibility and risk for rubella infection are highest among young adults. No large epidemics have occurred since the vaccine was licensed for use in 1969. However, outbreaks continue to occur among groups of susceptible persons who congregate in locations that increase their exposure, and among persons with religious and philosophic beliefs against vaccination. Several recent outbreaks have occurred in workplaces where most employees are foreign born, particularly from Latin America. 6 Reinfection can occur following natural or acquired immunity, but it is usually asymptomatic and only rarely accompanied by viremia.

Rubella virus is shed from the respiratory tract of infected persons beginning 10 days before the development of rash and for several days after the rash appears. The onset of the rash coincides with the period of maximal contagiousness, and infected persons are not considered infectious for more than 7 days after the rash appears. Infected infants shed virus for several months despite the presence of antibody.

Clinical syndromes Adult rubella is often asymptomatic.

Symptoms occur 12-23 days after exposure. Following a prodrome of fever and malaise, adults exhibit a maculopapular rash that begins on the face and extends downward, persists for 3-5 days, and often is accompanied by regional lymphadenopathy of the head and neck, which persists for days to weeks. One-third of adult women may develop arthritis in the fingers, knees, and wrists during the exanthematous phase of illness. Children develop hemorrhagic complications more often than adults. In contrast, encephalitis, albeit rare, is more common in adults and is fatal in 20-50% of cases.

Maternal rubella infection acquired in the first 20 weeks of gestation frequently results in congenital rubella. The earlier in pregnancy rubella occurs, the more severe the fetal consequences. Infection in the first trimester results in deafness, congenital heart disease, cataracts or glaucoma, endocrine abnormalities, and mental retardation in up to 60% of newborns. Spontaneous abortion also occurs commonly.

Treatment, prevention, and control Immunization of children and susceptible adults with live attenuated rubella virus effectively prevents rubella and accounts for the dramatic decline in the incidence of this disease in the United States. However, many adult women of childbearing age remain susceptible to rubella and require immunization prior to conception to prevent congenital rubella. The hemagglutination-inhibition serologic assay detects natural or acquired immunity. The Advisory Committee on Immunization Practices (ACIP) recommends screening of healthcare personnel who have not been vaccinated, and immunization of susceptible individuals. 7 Complications of rubella vaccine occur among adults and include lowgrade fever, symmetric polyarthralgias, distal paresthesias, lymphadenopathy, and rash. Vaccine is contraindicated in immunosuppressed persons and pregnant women. Pregnancy should be avoided for 3 months after vaccination (Table 22. 3).

Susceptible household contacts of infected adults and children pose a transmission risk in the workplace during the period of virus shedding, beginning about 10 days before the development of rash (about 1 week after exposure) until 7 days after rash appears. Therefore, susceptible individuals should not report to work during this time interval (Table 22. 2).

Epidemiology Tuberculosis (TB) is caused by Mycobacterium tuberculosis and, rarely today, by M. bovis. The incidence of tuberculosis (TB) in the United States declined steadily until the mid-1980s, but then sharply increased, especially in urban areas. The resurgence of TB in the United States in the late 1980s and early 1990s was associated with the emergence of multidrug-resistant TB (MDR-TB) and the HIV/AIDS epidemic. With this resurgence of TB in the United States came several high-profile nosocomial outbreaks associated with lapses in infection control practices and delays in diagnosis and treatment of persons with infectious TB, as well as the appearance and transmission of MDR-TB strains. Since 1992, the declines in the overall number of reported TB cases, including the level of MDR-TB, appear to reflect successful efforts to strengthen TB control following the resurgence of TB and the emergence of MDR-TB. 12 Activities emphasizing the first priority of TB control (i.e., promptly identifying persons with TB, initiating appropriate therapy, and ensuring completion of therapy) have been the most important factors in achieving this improvement. Such activities reduced community transmission of M. tuberculosis, particularly in areas with a high incidence of AIDS. Improvements in implementation of infection control measures in healthcare settings, concurrent with mobilization of the nation's TB control programs, succeeded in reversing the upsurge in reported cases of TB, and case rates have declined to their lowest levels to date. The threat of MDR-TB is decreasing, and the transmission of TB in healthcare facilities continues to abate due to implementation of infection controls and reductions in community rates of TB.

Nevertheless, some healthcare personnel are at risk for acquiring TB. Pulmonary TB is most commonly transmitted in healthcare settings by inhalation of aerosolized droplet nuclei derived from the respiratory secretions of patients with active respiratory TB. Close contact usually is required. Most other categories of workers generally are not at risk without close and sustained workplace contact with a person who has active untreated disease. Ingestion of unpasteurized milk from cows infected with M. bovis is no longer an important source of TB in most industrialized countries.

Clinical syndromes Primary infection usually is asymptomatic in adults. Teenagers and young adults are at higher risk for rapid progression to active disease, usually characterized by apical cavitary disease, than are older adults. Primary infection in the elderly usually is exhibited as lower lobe consolidation with hilar adenopathy. Primary tuberculosis in persons with advanced HIV infection is commonly symptomatic and progressive.

Once infection occurs, the organism may disseminate from the lungs to other sites, including the gastrointestinal and genitourinary tracts, and bone. Normally, the infection is contained by the host's immune response at this stage. The risk for reactivation is highest in the first year after exposure and declines thereafter. However, aging and stressors such as immunosuppression, intercurrent illness, and chronic malnutrition may increase the risk for reactivation or dissemination of the disease later in life. Clinically, reactivation tuberculosis usually is exhibited as upper lobe pulmonary cavitary disease, but virtually any organ system may be involved.

Treatment, prevention, and control Tuberculin skin testing allows determination of prior exposure to TB in immunologically healthy adults, by assessing delayed hypersensitivity to tuberculin antigens using purified protein derivative. The tuberculin skin test (TST) is the only proven method for identifying infection with M. tuberculosis in persons who do not have TB disease. Although the available TST antigens are neither 100% sensitive nor specific for detection of infection with M. tuberculosis, no better diagnostic methods have yet been devised.

The preferred skin test for diagnosing M. tuberculosis infection is the Mantoux test. It is administered by injecting 0.1 ml of 5 tuberculin units (TU) PPD intradermally into the dorsal or volar surface of the forearm. Tests should be read 48-72 h after test administration, and the transverse diameter of induration should be recorded in millimeters. There are three cut-off levels recommended for interpretation of the TST results. 14 In HIV-infected persons, any reaction resulting in an induration larger than 5 mm is read as positive. Among others, the presence of 15 mm or more of induration always indicates a positive test, 5-10 mm indicates a positive result in persons at risk for TB, and less than 5 mm is negative.

A positive TST means an individual has been exposed to TB in the past and is at risk for reactivation. A baseline chest radiogram should be performed on all persons with newly diagnosed TST positivity. If the x-ray study suggests active disease, sputum samples should be obtained, stained for acid-fast bacilli, and cultured for mycobacteria. Treatment should be implemented immediately if the index of suspicion is high. Public health officials should be notified to institute case management and evaluation of contacts in the home and work environment.

If the x-ray study is negative, treatment with isoniazid to suppress or eradicate latent organisms may be recommended, especially in persons younger than age 35 and for those who have recently converted to positive TSTs. 13 Although BCG vaccine is the most widely administered of all vaccines in the world, and has the highest coverage of any vaccine in the WHO Expanded Programme on Immunization, it appears to have had little epidemiologic impact on TB. Despite its shortcomings, and because of its beneficial effect in children and against leprosy, BCG vaccine likely will remain a component of childhood vaccination strategies in developing countries. However, because of questions about the vaccine's efficacy, and because it induces dermal hypersensitivity to purified protein derivative (PPD) tuberculin in most recipients, BCG has never been recommended for programmatic use in the United States. 14 Healthcare providers should follow appropriate infection control procedures, including use of isolation rooms and respiratory protection, when caring for patients with active tuberculosis. 15, 16 Varicella/zoster Epidemiology Varicella virus, the causative agent of chickenpox and zoster, is a highly contagious herpes virus spread by the respiratory route from person to person. The incubation period is about 14 days, and the period of infectivity begins a few days prior to the onset of the rash to about 6 days after the first crop of vesicles appears. Immunosuppression usually prolongs the period of infectivity, especially if varicella zoster immune globulin (VZIG) has been administered. Zoster represents reactivation of varicella virus that is latent in sensory nerve ganglia, and it is not a manifestation of primary infection except in newborns infected in utero. The incidence of zoster increases with age and immunosuppression. Susceptible persons in direct contact with zoster lesions risk developing primary varicella.

In the prevaccine era, varicella was endemic in the United States, and virtually all persons acquired varicella by adulthood. As a result, the number of cases occurring annually was estimated to approximate the birth cohort, or approximately 4 million per year. This incidence has likely decreased since licensure of the vaccine in 1995. Varicella is not a nationally notifiable disease, and surveillance data are limited. 17 Clinical syndromes Varicella in otherwise healthy children usually is a benign, self-limited disease characterized by low-grade fever and vesicular rash, often preceded by a viral prodrome. Varicella vesicles of primary infection appear first on the scalp and trunk and disseminate in crops showing various stages of development over the next 3-4 days. Healing results in crusting accompanied by intense pruritus. Manifestations of varicella are more severe in adults than in children. About 15% of adults with varicella show radiographic evidence of pulmonary involvement, but this is rarely clinically significant. However, cough, tachypnea, and impaired gas exchange can occur and persist for months after infection. Varicella during pregnancy can produce congenital varicella. In its most severe form, this infection can result in mental retardation, blindness, growth retardation, deafness, chorioretinitis, and a peculiar dermatomal lesion of the upper or lower extremity associated with limb atrophy.

Zoster, the most common manifestation of varicella infection among adults, characteristically produces unilateral vesicular eruptions preceded by pain in one to three dermatomes. Disseminated zoster, which is more likely in immunosuppressed patients, probably poses the same risk of infection transmission as primary varicella infection. The major complication of zoster is postherpetic neuralgia, which is especially common in the elderly and may be extremely debilitating. Zoster frequently produces cerebrospinal fluid pleocytosis and occasionally encephalitis. Immunologically healthy persons may experience recurrences of zoster, usually in the same dermatome as the initial outbreak. Zoster is a marker of deteriorating cellmediated immunity among HIV-infected patients, and it may disseminate.

Treatment, prevention, and control Passive immunization with VZIG is recommended for immunosuppressed susceptible persons, children with leukemia and other malignancies, and neonates exposed in utero within 5 days before delivery. 18 Several antiviral drugs are active against varicella zoster virus, including acyclovir, valacyclovir, famciclovir, and foscarnet. 18 Famciclovir and valacyclovir are approved for use only in adults. Clinical studies indicate that these drugs may be beneficial if given within 24 hours of onset of rash, resulting in a reduction in the number of days new lesions appeared, in the duration of fever, and in the severity of cutaneous and systemic signs and symptoms. Antiviral drugs have not been shown to decrease transmission of varicella, reduce the duration of absence from school, or reduce complications. Oral acyclovir can be considered in otherwise healthy adolescents and adults or secondary cases in the household, because of the increased risk of severe illness in these groups. Antiviral therapy may also be considered for persons with chronic cutaneous or pulmonary disorders, persons receiving long-term salicylate therapy, and for children receiving short, intermittent or aerosolized courses of corticosteroids. Antiviral drugs are not recommended for routine postexposure prophylaxis. Systemic steroids in older adults (more than 60 years old) may reduce the incidence and severity of postherpetic neuropathy if started early (within 5 days of skin manifestations).

Varicella has been difficult to prevent because of the high degree of contagion in households, schools, and healthcare settings. Live attenuated virus vaccines have demonstrated efficacy in preventing primary infection, and one was licensed for use in the United States in 1995. Routine immunization is now recommended for children less than 18 months of age. 17 Varicella vaccination should be given to susceptible adolescents and adults who are at high risk of exposure to varicella. This group includes persons who live or work in environments in which there is a high likelihood of transmission of varicella, such as teachers of young children, residents and staff in institutional settings, and military personnel. Varicella vaccination is also recommended for susceptible adolescents and adults who will have close contact with persons at high risk for serious complications of acquired varicella, including healthcare personnel and susceptible family contacts of immunocompromised individuals. The ACIP recommends that all healthcare personnel be immune to varicella, either from a reliable history of prior varicella infection or vaccination, to reduce the risk of infection and its complications, and to decrease the possibility of transmission of varicella zoster virus to patients (Table 22. 3). Susceptible adults exposed to children with varicella or with disseminated zoster pose a risk of transmitting varicella to non-immune coworkers, and they should not work until the incubation period is over or, if they become ill, until all lesions are crusted (Table 22. 2). Dermatomal zoster is not spread efficiently by the air-borne route and otherwise healthy adults afflicted with this illness may be allowed to work if they can avoid touching the lesions and contaminating the work environment. The role of vaccine in the postexposure management of susceptible employees needs to be elucidated. Data from the United States and Japan in a variety of settings indicate that varicella vaccine is effective in preventing illness or modifying the severity of illness if used within 3 days, and possibly up to 5 days, of exposure. ACIP recommends vaccine be used in susceptible persons following exposure to varicella. 17 Personnel should be excluded from work who have onset of varicella until all lesions have dried and crusted (Table 22. 2).

Following exposure to varicella, personnel who are not known to be immune to varicella (by history or serology) should be excluded from duty beginning on the 10th day after the first exposure until the 21st day after the last exposure (28th day if VZIG was given).

Epidemiology Acute gastrointestinal infection follows upper respiratory illness as the next leading category of infectious diseases causing absenteeism among adult workers. A wide array of pathogens, including viruses, bacteria, and protozoa, can result in acute infections of the stomach, small bowel, or colon. A comprehensive discussion of enteric pathogens is provided in Chapter 54 (Waterborne Microbial Diseases). Most of the etiologic agents are acquired by the fecal-oral route; produce mild, self-limited diseases; and resolve without specific therapy. Agents of dysentery (e.g., Shigella spp.) often are highly transmissible through low-inoculum exposures. Occupational transmission of food-borne or water-borne illnesses occurs; person-to-person transmission has propagated outbreaks of many of these illnesses in healthcare settings, daycare and nursery schools, and institutions where sanitation is poor. Instances of such transmission have generally involved food handlers, who are often poorly trained and short-term employees, serving as sources of transmission to others. Occupations requiring travel to countries with poor sanitation present a major risk for gastrointestinal infections. Poultry workers are frequently exposed to salmonella infections.

Avoidance of oral contact with sources of fecal contamination is the most important strategy for preventing transmission of pathogens associated with intestinal infections. Maintaining good personal hygiene, including careful hand hygiene after using restrooms and before food preparation; proper cooking and storage of foods; and avoidance of contaminated foods and water when traveling are essential prevention strategies. Food handlers with diarrheal illnesses should not work until symptoms have resolved, and cure of bacterial infections should be documented by obtaining negative stool cultures more than 48 hours after antimicrobial therapy is completed (Table 22. 2). The only vaccines for any of the etiologic agents for acute enteric infections are for typhoid and hepatitis A, which are recommended for personnel in laboratories who frequently work with Salmonella typhi or hepatitis A virus (Table 22. 3).

Epidemiology Cytomegalovirus (CMV) is a ubiquitous herpes virus transmitted by direct inoculation with infected body fluids (including blood, blood products, respiratory secretions, saliva, and urine) and through sexual contact with infected partners. At least 40% of healthy adults have serologic evidence of prior CMV infection. Infection can be acquired perinatally, in utero during maternal primary infection, during birth by passage through infected vaginal secretions, or through ingestion of infected breast milk. CMV is known to be highly transmissible in daycare centers and nursery schools. Sexually active adults and recipients of blood products are also at high risk for infection.

Infants and young children excrete CMV in their urine, saliva, and respiratory secretions for several months after infection. Virus is much less readily detected in healthy adults, but intermittent shedding has been documented. Like all herpes viruses, CMV remains latent in the host after initial infection. Previously infected persons may be reinfected with new strains of CMV.

Occupational transmission of CMV has been documented in childcare settings, where person-to-person spread through exposure to infected secretions and urine is believed to provide an efficient mode of transmission. Up to 50% of seronegative workers in preschool daycare centers have acquired CMV infection in some studies, indicating a potentially serious risk to women of child-bearing age, because of the adverse effects of primary maternal CMV infection on the fetus. At one time, employment in healthcare settings also was believed to pose a high risk for CMV acquisition. However, epidemiologic investigations suggest that most infections in healthcare personnel are acquired sexually, or from exposure to young children in the home, and not from work-related contact.

is asymptomatic in healthy persons. A self-limited mononucleosis-like illness occurs in a minority, which may be complicated by hepatitis, pneumonitis, hematologic abnormalities, and myocarditis.

Immunosuppressed children and adults with primary CMV infection, reactivation, or reinfection may develop severe sequelae. Organ transplant recipients, HIV-infected patients, and persons with malignancies have a risk of developing CMV viremia, pneumonia, hepatitis, pancreatitis, enteritis, and retinitis.

Primary CMV infection at any stage of pregnancy carries a greater risk to the fetus than does recurrent CMV infection during pregnancy. Symptoms of congenital CMV infection may be present at birth, and are due to the consequences of active virus replication and resultant end-organ damage. Congenital cytomegalic inclusion disease, the most severe form of this entity, includes central nervous system disease, respiratory distress, hepatitis, hepatosplenomegaly, rash, and multi-system failure. Infection acquired from exposure to cervical CMV during birth usually is asymptomatic and detected by the onset of virus shedding 4-8 weeks postpartum.

with ganciclovir or foscarnet for CMV infection is reserved for immunosuppressed persons at high risk for severe complications. The safety and effectiveness of these agents in preventing congenital CMV have not been established.

Avoidance of mucosal contact with infected body fluids is the best strategy for preventing CMV transmission. Hand washing after contact with secretions and fomites is essential, especially in nurseries and daycare settings.

The presence of persons at risk for CMV shedding in the workplace does not pose a hazard to other employees unless direct contact with infected secretions is anticipated. Isolation of infected neonates or children is not essential if hand washing is performed after contact with secretions, blood, and urine. Pregnant healthcare providers compliant with hand washing protocols can generally safely care for patients with CMV infection. [19] [20] [21] No work restriction is necessary for individuals with CMV infection (Table 22 .2).

direct exposure to blood and other infected body fluids. Children born to infected mothers are at high risk for HBV infection. Persons parenterally exposed to blood, including multi-transfused patients, hemophiliacs, dialysis patients, and injection drug users, also are at significant risk. Sexual contact with infected partners is another efficient mode of HBV spread. In most industrialized countries, adult infections usually are acquired sexually or by injection drug use.

HBV is a relatively hardy virus capable of surviving on environmental surfaces and fomites. Transmission in households is well documented and may, in part, be attributable to mucosal contact with fomites contaminated with secretions or blood from infected persons.

Healthcare personnel and others at risk for occupational blood exposure through percutaneous, mucosal, or dermal routes can acquire HBV infection. The risk associated with accidental needle-stick inoculation of infected blood to susceptible healthcare personnel varies between 5% to 35%, depending on the hepatitis B e antigen (HBeAg) status, and hence the viral titer of the source. In up to 50% of occupational infections, a discrete exposure cannot be identified.

Hepatitis B has an incubation period of 40-180 days. The period of infectivity precedes the development of jaundice by 2-7 weeks and correlates with the presence of hepatitis B surface antigen (HBsAg) in the serum; 5-10% of persons with acute (but often clinically silent) infection develop chronic antigenemia. In the United States, up to 1% of adults are carriers of HBV, and provide a reservoir for maintenance of the disease in the population.

apparent hepatitis in about one-third of acutely infected adults. Clinical hepatitis may be preceded by a prodrome of fever, malaise, urticarial or maculopapular rash, and arthralgias for several days. Fever usually resolves before the onset of jaundice. Jaundice, dark urine, and scleral icterus usually are present by the time patients seek medical attention. Right upper quadrant tenderness, mild hepatic enlargement, and occasionally, splenomegaly are signs that should suggest the diagnosis. The most striking laboratory abnormality is the finding of extreme elevations in the aminotransferase enzymes. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) may be elevated to more than 10 times the normal levels, whereas the bilirubin and alkaline phosphatase levels are increased to a much lesser extent.

Fulminant liver involvement occurs in about 1% of adults and may be complicated by more serious abnormalities, including hypoglycemia, coagulopathy, and hypoalbuminemia. Hepatic encephalopathy, hepatorenal syndrome, and bleeding diatheses are life-threatening complications seen in these patients. About 10% of adults with clinically apparent acute HBV infection proceed to chronic HBs-antigenemia, and are at risk for chronic hepatitis, postnecrotic cirrhosis, and primary hepatocellular carcinoma.

Patients with asymptomatic primary HBV infection are at higher risk for chronic infection than those with symptomatic infection. While chronic persistent hepatitis, a benign illness of little clinical consequence except for the potential for HBV transmission to susceptible individuals, may occur, the major health concern is chronic active hepatitis, which eventually may produce cirrhosis, liver failure, and hepatoma.

Hepatitis B is differentiated from other causes of hepatitis by serologic assays. 23 A positive hepatitis B surface antigen (HBsAg) test identifies patients with current infection and correlates with infectivity during acute and chronic infection. Titers of HBsAg in the chronic phase of illness may wax and wane and occasionally fall below the limits of laboratory detection, so sequential testing should be performed if chronic HBV is suspected. The presence of HBeAg correlates with active virus replication and is a marker of high infectivity and high titer of HBV in the liver and blood. Antibody to hepatitis B surface antigen (HBsAb) appears when HBsAg is cleared and is positive in individuals with immunity after recent or prior infection or immunization. Persons with HBsAb are not susceptible to acute infection or chronic hepatitis B, except in the very rare case in which reinfection occurs with a strain of hepatitis B against which the normal antibody response does not provide cross-protection. Hepatitis B core antibody (HBcAb) appears before HBsAb and just after HBsAg is cleared from the serum, and this is a useful test for diagnosing acute hepatitis B in the window period before HBsAb appears. High titers of HBcAb persist in chronically infected persons and obviously do not predict immunity from further liver disease.

There currently is no treatment for acute hepatitis B. Alpha interferon and lamivudine have been licensed for the treatment of persons with chronic hepatitis B. These drugs are effective in up to 40% of cases.

HBV infection is largely preventable. Inoculation with recombinant vaccines containing HBsAg components is safe and highly immunogenic, and appears to confer protection from infection for at least 12 years (Table 22. 2). Postvaccination testing should be done 1-2 months after completion of the three-dose series to document an appropriate response (i.e., > 10 mIU/ml). 23 More than 90% of persons immunized with three properly timed doses (e.g., 0, 1, and 6 months) of vaccine administered intramuscularly in the deltoid region develop protective HBsAb levels. Factors associated with a lack of response include improper vaccination (improperly stored vaccine, gluteal inoculation, subcutaneous injection), obesity, older age, and smoking. Persons who do not respond to the primary vaccine series should receive a second three-dose series or be evaluated for HBsAg positivity.

Since 1982, substantial progress has been made toward eliminating HBV transmission in children and reducing the risk for HBV infection in adults. 24 Recommendations of ACIP have evolved from universal childhood vaccination, to prevention of perinatal HBV transmission, vaccination of adolescents and adults in high-risk groups, and catch-up vaccinations for susceptible children in high-risk populations. 25, 26 The ACIP vaccination strategies for children and adolescents have been implemented successfully in the United States, and routine immunization of all children is now recommended. The Occupational Safety and Health Administration's (OSHA's) Blood-borne Pathogen Standard mandates provision of vaccine at no cost to all healthcare employees and others at occupational risk for blood exposure. 27 Substantial declines in the incidence of acute hepatitis B have occurred among highly vaccinated populations, such as young children and healthcare personnel. Vaccine should also be provided to susceptible individuals before sexual maturity, particularly to teenagers in those settings (e.g., inner cities, concentration of poverty) where HBV is highly prevalent, and to all adults at risk for sexual or occupational exposure.

Preimmunization screening for evidence of prior or persistent infection usually is not cost effective. However, postimmunization testing for antibody response is recommended 1-2 months after the 3 rd dose to detect nonresponders among persons at high risk for exposure. Titers of HBsAb fall over time and may be undetectable after 5-10 years. The duration of vaccine protection is under investigation. Most data suggest that protection persists even when HBsAb titers fall below the level of detection, and routine screening and boosting are not recommended.

The need for prophylaxis for persons sustaining accidental percutaneous or mucosal exposures to blood should be based on several factors, including the HBsAg status of the source, and the hepatitis B vaccination and vaccineresponse status of the exposed person. Such exposures usually involve persons for whom hepatitis B vaccination is recommended. Any blood or body fluid exposure to an unvaccinated person should lead to initiation of the hepatitis B vaccine series. A summary of prophylaxis recommendations for percutaneous or mucosal exposure to blood according to the HBsAg status of the exposure source and the vaccination and vaccine-response status of the exposed person is shown in Table 22 .4. 23 When hepatitis B immune globulin (HBIG) is indicated, it should be administered as soon as possible after exposure (preferably within 24 hours). The effectiveness of HBIG when administered more than 7 days after exposure is unknown. When hepatitis B vaccine is indicated, it § Hepatitis B immune globulin; dose is 0.06 ml/kg intramuscularly. ¶ A responder is a person with adequate levels of serum antibody to HBsAg (i.e., anti-HBs ≥10 mIU/ml). ** A non-responder is a person with inadequate response to vaccination (i.e., serum anti-HBs <10 mIU/ml). † † The option of giving one dose of HBIG and reinitiating the vaccine series is preferred for non-responders who have not completed a second three-dose vaccine series. For persons who previously completed a second vaccine series but failed to respond, two doses of HBIG are preferred. § § Antibody to HBsAg. should also be administered as soon as possible (preferably within 24 hours) and can be administered simultaneously with HBIG at a separate site (vaccine should always be administered in the deltoid muscle).

For exposed persons who are in the process of being vaccinated but have not completed the vaccination series, vaccination should be completed as scheduled, and HBIG should be added as indicated (Table 22 .4). Persons exposed to HBsAg-positive blood or body fluids who are known not to have responded to a primary vaccine series should receive a single dose of HBIG and reinitiate the hepatitis B vaccine series with the first dose of the hepatitis B vaccine as soon as possible after exposure. Alternatively, they can receive two doses of HBIG, one dose as soon as possible after exposure, and the second dose 1 month later. The option of administering one dose of HBIG and reinitiating the vaccine series is preferred for non-responders who did not complete a second three-dose vaccine series. For persons who previously completed a second vaccine series but failed to respond, two doses of HBIG are preferred. 23

States. It is estimated that 1.8% of Americans have been infected with HCV. HCV-associated end-stage liver disease is the most frequent indication for liver transplantation among US adults. 28 The incubation period for acute HCV infection ranges from 2 to 24 weeks (averaging 6-7 weeks). HCV transmission occurs primarily through exposure to infected blood, such as through injection drug use, blood transfusion, solid organ transplantation from infected donors, unsafe medical practices, occupational exposure to infected blood, and birth to an infected mother (i.e., vertical transmission). HCV may also be acquired through sexual contact, but the importance of this mode of transmission in the United States is not well characterized. HCV is not transmitted efficiently through occupational exposures to blood. Healthcare personnel who are parenterally exposed to infected blood through needlestick injuries may acquire HCV infection, but the magnitude of risk (approximately 2 in 100 HCV needlesticks) is less than that associated with HBV exposure. One epidemiologic study indicated that transmission occurred only from hollow-bore needles compared with other sharps. Transmission rarely occurs from mucous membrane exposures to blood, and no transmission in HCV has been documented from skin exposures to blood. Data are limited on survival of HCV in the environment.

In contrast to HBV, the epidemiologic data for HCV suggest that environmental contamination with blood containing HCV is not a significant risk for transmission in the healthcare setting, with the possible exception of the hemodialysis setting where HCV transmission related to environmental contamination and poor infection control practices have been implicated. The risk for transmission from exposure to fluids or tissues other than HCV-infected blood also has not been quantified but is expected to be low. HCV is not known to be transmissible through the airborne route, through casual contact in the workplace, or by fomites.

Clinical syndromes Hepatitis C virus infection produces a spectrum of clinical illness similar to HBV and is indistinguishable from other forms of viral hepatitis based on clinical symptoms alone. Serologic tests are necessary to establish a specific diagnosis of hepatitis C. Most adults acutely infected with HCV are asymptomatic. After acute infection, 15-25% of persons appear to resolve their infection without sequelae as defined by sustained absence of HCV RNA in serum and normalization of ALT levels. 28 Chronic HCV infection develops in most persons (75-85%), with persistent or fluctuating ALT elevations indicating active liver disease developing in 60-70% of chronically infected persons. No clinical or epidemiologic features among patients with acute infection have been found to be predictive of either persistent infection or chronic liver disease. Moreover, various ALT patterns have been observed in these patients during follow-up, and patients might have prolonged periods (greater than or equal to 12 months) of normal ALT activity even though they have histologically confirmed chronic hepatitis. Thus, a single ALT determination cannot be used to exclude ongoing hepatic injury, and long-term follow-up of patients with HCV infection is required to determine their clinical status and prognosis.

The course of chronic liver disease is usually insidious, and progresses slowly without symptoms or physical signs in the majority of patients during the first two or more decades after infection. Chronic hepatitis C frequently is not recognized until asymptomatic persons are identified as HCV positive during blood donor screening, or elevated ALT levels are detected during routine physical examinations. Most studies have reported that cirrhosis develops in 10-20% of persons with chronic hepatitis C over a period of 20-30 years, and HCC in 1-5%, with striking geographic variations in rates of this disease. However, when cirrhosis is established, the rate of development of HCC might be as high as 1-4% per year. Longer follow-up studies are needed to assess lifetime consequences of chronic hepatitis C, particularly among those who acquired infection at young ages.

Although factors predicting severity of liver disease have not been well defined, recent data indicate that increased alcohol intake, being aged greater than 40 years at infection, and being male are associated with more severe liver disease. In particular, among persons with alcoholic liver disease and HCV infection, liver disease progresses more rapidly; among those with cirrhosis, a higher risk for development of HCC exists. In addition, persons who have chronic liver disease are at increased risk for fulminant hepatitis A.

Screening enzyme immunoassay (EIA) and supplemental confirmatory immunoblot tests are licensed and commercially available to detect antibodies to HCV (anti-HCV). Anti-HCV may be detected within 5-6 weeks after the onset of infection but a single anti-HCV test cannot distinguish between acute, chronic, or past infection. HCV RNA can be detected within 1-2 weeks of exposure to the virus and several weeks before elevations of ALT and detection of anti-HCV. Testing for anti-HCV by EIA is recommended 4-6 months after an exposure to detect infection; testing for HCV RNA may be performed 4-6 weeks after exposure if earlier detection of infection is desired. 23 Treatment, prevention, and control HCV-positive patients should be evaluated for the presence and severity of chronic liver disease. Initial evaluation for presence of disease should include multiple measurements of ALT at regular intervals, because ALT activity fluctuates in persons with chronic hepatitis C. Patients with chronic hepatitis C should be evaluated for severity of their liver disease and for possible treatment. Alpha interferon (with or without ribavirin) treatment of HCV appears to prevent HCV replication, decrease hepatic inflammation, and improve symptoms among chronically infected persons. Persons with chronic HCV have undergone successful liver transplantation, although recurrences have been documented in this setting. Antiviral therapy is recommended for patients with chronic hepatitis C who are at greatest risk for progression to cirrhosis. These persons include anti-HCV-positive patients with persistently elevated ALT levels, detectable HCV RNA, and a liver biopsy that indicates either portal or bridging fibrosis or at least moderate degrees of inflammation and necrosis. Therapy for hepatitis C is a rapidly changing area of clinical practice and consultation with a knowledge specialist (e.g., hepatologist) is recommended. 29 No clinical trials have been conducted to assess postexposure use of antiviral agents (e.g., interferon with or without ribavirin) to prevent HCV infection, and antivirals are not FDA approved for this indication. Available data suggest that an established infection might need to be present before interferon can be an effective treatment. 23, 29 Because there is currently no postexposure prophylaxis (PEP) for HCV, the intent of recommendations for postexposure management is to achieve early identification of infection and, if present, referral for evaluation of treatment options. In addition, no guidelines exist for administration of therapy during the acute phase of HCV infection. However, limited data indicate that antiviral therapy might be beneficial when started early in the course of HCV infection. When HCV infection is identified early, the person should be referred for medical management to a specialist knowledgeable in this area. 23 At present, avoidance of parenteral exposure to blood is the only available strategy for preventing HCV infection.

Epidemiology It is estimated that more than 60 million persons worldwide had been infected by HIV and that 40 million were living with HIV/AIDS by the end of the year 2000. 30 In the United States, almost 1 million persons are living with HIV. 30 Most individuals with HIV infection are active adults employed in the workforce. The primary means of acquiring infection among adults is either through behaviors such as unprotected homosexual or heterosexual intercourse with an infected partner, involving the exchange of body fluids, or injecting drug use involving shared needles and syringes. The virus also is perinatally transmitted to approximately 20-40% of children born to infected mothers, (e.g., vertical transmission). Breastfeeding is a bidirectional mode of transmission, to nursing infants of infected mothers and, rarely, to mothers of nursing infants when nipple maceration and biting occur. Since 1985, all donated blood in the United States has been screened for HIV infection. The risk of HIV infection due to transfusion of blood products screened by current methods is estimated to be 1 in 1,900,000 units transfused. 32 Screening does not completely eliminate the potential for a seronegative but infected unit from a recently infected donor to escape detection.

HIV is not transmitted by the air-borne route, by household or workplace contact with infected persons, by exposure to contaminated environmental surfaces, or by insect vectors. The virus is easily inactivated by most common disinfectants, including household bleach (diluted 1:100).

Commercial sex workers are at the greatest risk of acquiring HIV infection occupationally. The other group of workers at risk for acquiring HIV infection occupationally is healthcare personnel. Healthcare providers and other workers in contact with blood or other body fluids who sustain accidental percutaneous or mucosal inoculations with virus-infected material are at risk for infection. The magnitude of risk depends on the severity of exposure, but on the average, about 1 in 300 HIV needlesticks results in infection. The risk for infection following mucosal exposures is estimated to be lower at approximately 0.09%. In the absence of direct exposure, healthcare providers are not at occupational risk for HIV infection. In the United States, through December 2002, there have been 57 cases of occupationally acquired HIV infection reported with an additional 139 possible cases. 32 Clinical syndromes The clinical course of HIV infection is variable and changing with the advent of antiretroviral therapy, as well as treatment and prophylaxis for infectious complications. Early after infection, within a few weeks to months, an acute febrile illness characterized by malaise, pharyngitis, lymphadenopathy, maculopapular rash, and headache may occur. The frequency of this mononucleosis-like illness has varied widely in reports of seroconverting individuals. At initial presentation of such patients, HIV antibody screening tests (enzyme immunoassay (EIA)) may be negative, but viral antigen (p24 antigen) and serologic reactivity to one or more viral components (Western blot test) allows the diagnosis to be established at this stage. HIV infection should be suspected in any person with a mononucleosis syndrome lacking a positive heterophil antibody response (monospot test).

Following initial infection, most persons have generalized asymptomatic lymphadenopathy and appear well. However, laboratory tests document a gradual decline in the number of circulating T-helper lymphocytes (CD4 cells), beginning soon after infection and continuing over the next several years. T-helper cells are essential components of the immune system and mediate aspects of both cellular and humoral immunity.

Symptoms, signs, and illness suggestive of mild to moderate immunodeficiency appear after about 5 years, when CD4 cells decrease by about 50%, to less than 500 cells/dl. Intermittent fever, oral thrush, bacterial pneumonia, enteric infections, and reactivated TB are typically diagnosed at this time. Signs suggestive of more rapid deterioration include oral hairy leukoplakia (a wart-like white growth in the oral cavity), shrinking lymphadenopathy, fever, weight loss, and elevated erythrocyte sedimentation rate. When CD4 cell counts fall below 200, serious opportunistic infections can be anticipated. Pneumocystis pneumonia (PCP) was the most common index diagnosis in the first 5 years of the epidemic, but the advent of effective PCP prophylaxis has altered the picture. Other opportunistic infections and malignancies, including Kaposi's sarcoma, lymphoma, disseminated TB, toxoplasmosis, and cryptococcal meningitis, now account for the majority of index HIV diagnoses.

With the exception of TB, the infectious complications of HIV infection generally are not transmissible to healthy individuals and pose no risk in the workplace. Indeed, the causative organisms are ubiquitous and most adults have already been exposed. Opportunistic infections in HIVinfected patients usually represent reactivation of dormant organisms when the immune system can no longer keep them inactive.

be offered to all patients with symptoms ascribed to HIV infection. 34 Recommendations for offering antiretroviral therapy in asymptomatic patients require analysis of many real and potential risks and benefits. Information regarding treatment of acute HIV infection from clinical trials is very limited. Ongoing clinical trials are addressing the question of the long-term clinical benefit of potent treatment regimens for primary infection. In general, treatment should be offered to individuals with fewer than 350 CD4 T cells/mm or plasma HIV RNA levels exceeding 55,000 copies/rnL (by RT-PCR or bDNA assay). Once the decision has been made to initiate antiretroviral therapy, the goals should be maximal and durable suppression of viral load, restoration and/or preservation of immunologic function, improvement of quality of life, and reduction of HIVrelated morbidity and mortality. 33 HIV-infected individuals found to have latent TB infection should be treated with antituberculous therapy to prevent activation of disease. 13 Persons at risk for direct contact with blood and other potentially infected materials should receive specific instruction in universal/standard precautions for infection control, as recommended by the Centers for Disease Control and Prevention 34, 35 and mandated by the Occupational Safety and Health Administration. 27 For most environments outside healthcare settings, common sense and attention to personal hygiene are adequate to protect workers. Gloves should be worn to clean up visible sites of blood contamination. Environmental surfaces can then be decontaminated with disinfectant solutions or household bleach (diluted 1:100). 34, 36 Individuals sustaining accidental parenteral exposures to HIV should be counseled to undergo baseline and followup testing for 6 months after exposure (e.g., 6 weeks, 3 months, and 6 months) to diagnose occupational infection. Postexposure chemoprophylaxis with antiretroviral agents has been recommended by the US Public Health Service since 1996 after certain exposures to HIV-infected sources which pose a risk of infection transmission, such as needlesticks, mucous membrane, and non-intact skin exposures (Tables 22.5 and 22.6). Data from animal models of prophylaxis with these agents suggest that antiviral activity is diminished when treatment is delayed for more than 24 hours. For this reason, immediate reporting and access to chemoprophylaxis is recommended. Occupational exposure is a frightening experience. Consultation with clinicians knowledgeable about HIV transmission risks who can provide supportive counseling to the worker is essential during the follow-up interval. CDC recommends that occupationally exposed workers refrain from unsafe sexual practices, pregnancy, and blood and organ donation for 6 months after exposure to minimize the risk of transmission.

Zoonoses are infections that are maintained in nature by transmission between vertebrate animals, and they can be transmitted from other vertebrates to humans or from humans to other vertebrates. Zoonotic pathogens can be divided into two major groups: (1) those transmitted primarily among wild animals (e.g., Yersinia pestis, rabies), and (2) those transmitted primarily among domestic animals (e.g., Sporothrix schenkii, non-typhoid Salmonella spp.). Other infections not properly classified as zoonoses can result from working directly with animals (e.g., infected wounds resulting from animal bites) or with animal products (e.g., anthrax in carpet weavers). Many zoonotic infections present occupational risks, not only to those who work with live or dead vertebrate animals or animal products but also to workers exposed to certain environments contaminated by animals or animal products.

Thus, workers in veterinary medicine, animal husbandry, and animal research are at risk for acquiring a host of zoonotic infections specific to the type of live animal exposure, just as those involved in healthcare work with humans are at risk for infections acquired from humans. Examples of such zoonotic infections include Q fever in veterinarians, psittacosis (caused by Chlamydia psittaci) in duck farmers, orf (contagious ecthyma) in shepherds, lymphocytic choriomeningitis (e.g., leptospirosis) in laboratory workers who handle rodents, fatal herpes virus simiae infection in primate handlers, and more recently, monkeypox in veterinarians and pet store owners. 37, 38 Influenza A (H5Nl) (avian flu) infection was shown to have been transmitted from ducks and chickens to poultry workers in Hong Kong and has become an important source of epidemic infection in various international settings; 39 lyssavirus (related to rabies virus) infections have been transmitted from bats to humans in Australia, 41 and a large outbreak of febrile encephalitic and respiratory illnesses among workers who had exposure to pigs was shown to be due to infection with a previously unrecognized paramyxovirus (formerly known as Hendra-like virus, now called Nipah virus). 41 Brucellosis is an example of a zoonotic infection in abattoir workers exposed to live or dead animals or animal products. Examples of zoonotic infections acquired by workers exposed to environments harboring or contaminated by contagious animals include leptospirosis in rice field workers, and Argentine hemorrhagic fever typically acquired by adult males harvesting corn in cornfields inhabited by rodents, which serve as the reservoir for Junin or Machupo virus.

It is beyond the scope of this chapter to review the large number of zoonoses (about 200 have been described) that could pose a risk to workers in unique jobs that involve contact with various animals or environments. For each type of occupation that involves regular animal contact, it is important to recognize the types of infectious disease risks involved, consider baseline studies and storage of serum for future serologic tests if risks are high, plan preventive measures when possible, and prepare for early diagnosis and treatment of such infections when illness occurs. 42 Some of the zoonoses, the occupational groups they affect, and their clinical presentations are included in Table 22 .1.

Infectious diseases continue to emerge, posing threats to the health of workers in numerous settings. A prime example of such a threat is severe acute respiratory syndrome or SARS, first identified in early 2003 and responsible for illness and death primarily among exposed healthcare personnel. 43 Emerging infectious issues which may prove to be challenges for occupational health include those posed by bioterrorism, biotechnology, 44 and emerging and reemerging infections. These emerging infections emphasize the need for continued vigilance and for careful history taking about occupational exposures when evaluating individuals for illnesses that could possibly be occupationally acquired. Timeliness in identification and reporting of cases assists in the accurate estimation of the magnitude of the infectious disease problem and in the development of additional preventive and therapeutic measures.

Screening of employees for infection with or susceptibility to infectious diseases is an important part of healthcare maintenance, especially when the occupational setting poses a significant risk of transmitting or acquiring infections. Screening also is warranted if specific interventions are available to prevent disease transmission among workers. Assessment of behaviors, such as smoking, that increase the risk of acquiring infections also is valuable so that employees can be provided educational and other interventions to modify risks.

Preventing infectious diseases in workers can decrease absenteeism and financial costs associated with disability, sick leave, and health insurance, even if the primary source of infection is non-occupational. Attending to these issues at the time of employment obviates the need for ongoing surveillance of many infections and simplifies outbreak investigations by documenting the pre-exposure immune status of contacts.

TST screening for active disease identifies those persons who would benefit from prophylaxis (Tables 22.5 and 22.6). 14 TB vaccination with bacillus of Calmette-Guerin (BCG) vaccine, a live attenuated strain of M. bovis, is provided for children and some workers in most European countries, but it is not recommended in the United States because of its unproven efficacy when used in adults and because it induces dermal hypersensitivity to purified protein derivative (PPD) tuberculin in most recipients, impeding the usefulness of TST as a screening tool.

Persons age 65 years and older, persons with chronic diseases or pulmonary disorders, and healthcare personnel should be offered pneumococcal vaccine and annual influenza vaccine (Table 22. 3). 45 Rubella immune status should be ascertained and men and women immunized in settings where women of childbearing age are employed (Table 22. 3). Even though rubella is not often transmitted in the workplace, outbreaks can occur among susceptible individuals and vaccination is an important public health intervention. Medical personnel should demonstrate proof of rubella immunity or vaccination prior to patient contact.

Measles vaccine should be provided to all workers born after 1957 with no documented history of measles who have not received two injections of live virus vaccine (Table 22. 3). Screening for immunity to varicella and mumps is not routinely recommended, except for healthcare providers and adults with no history of infection with these agents who are exposed to young children.

All adults require tetanus immunization. Tetanus diphtheria toxoid (Td) boosters should be administered every 10 years to adults who have completed primary immunization (Table 22. 3). Employees with no prior history of tetanus diphtheria immunization or with uncertain histories should receive a series of three primary vaccine injections. 45 Similarly, adults with no history of polio immunization should undergo primary immunization with inactivated polio vaccine, especially if they are employed in healthcare settings or when travel to endemic areas is anticipated.

Persons employed in occupations that pose a risk for parenteral contact with blood and other body fluids should be offered hepatitis B immunization (Table 22. 3). Healthcare personnel, laboratory workers, animal handlers, first responders, and personal service workers such as barbers, tattooists, and cosmetologists are included in this category. Adults with multiple sexual partners also should be encouraged to undergo immunization. Serum banking to allow documentation of baseline serostatus is useful for laboratory and healthcare personnel at risk for other bloodborne infections such as HIV or more exotic infections.

Laboratory workers and animal handlers may be at risk for unusual infectious diseases. Q fever, a rickettsial disease transmitted by the air-borne route, is a special risk encountered by handlers of sheep and similar animals. Serologic testing for Q fever titers prior to occupational exposure is important to document baseline status and to detect seroconversion at follow-up testing. Although smallpox vaccine is no longer recommended routinely, genetically engineered vaccines prepared from vaccinia may pose a risk to researchers and clinicians treating patients enrolled in vaccine trials. Laboratory workers who handle vaccinia or recombinant vaccinia preparations in culture or in animals should receive vaccinia vaccine. Healthcare personnel caring for patients immunized with vaccinia or other orthopoxviruses or tissues and specimens from patients with these infections also should be immunized. A program for smallpox vaccination for selected individuals who may be in the frontline for responding to a bioterrorist attack has recently been initiated in the United States. 46 Consultation should be obtained to determine the need for screening, immunization, and testing for other exotic infections.

Some animal handlers are at risk of acquiring rabies through bites or exposure to infected secretions and tissues. Immunization with human diploid cell vaccine (three 1-ml intradermal doses on day 0, 7, and 21 or 28) should be provided to workers at risk for rabies and for persons traveling for more than 1 month to areas where rabies is endemic (Table 22. 3). Booster injections should be provided every 2 years for those with continuing exposure.

Surveillance of infectious diseases is conducted to detect increased occurrence of disease so that preventive interventions can be initiated. Surveillance can be passive (based on employee health consultations or reports from contractual providers or supervisors) or active (actual monitoring of disease occurrence).

Active surveillance for infectious diseases is not required in most occupational settings. In work environments where exposure to M. tuberculosis may occur -such as healthcare settings, residential care facilities, shelters, and correctional facilities -active TST surveillance among susceptible individuals is indicated. Periodic TSTs are especially important in the wake of several recent outbreaks associated with drug-resistant strains of M. tuberculosis in hospitals, adult care settings, and home healthcare settings. 16 Skin testing should be performed at least annually in these settings, and perhaps as often as every 6 months, for personnel at high risk for exposure to active TB. Surveillance of teachers, travelers to endemic areas, and employees in other institutional settings where close contact with infected individuals is possible also may be warranted, depending on the local prevalence of TB. 14 Surveillance for infections among laboratory workers and animal handlers exposed to specific pathogens should be individualized in accordance with standard guidelines for biosafety in microbiologic and biomedical laboratories. 47 Maintaining standardized records of reportable infectious diseases is an important component of passive surveillance in the workplace. Centralized collection and assessment of these records at regular intervals may allow early detection of outbreaks of occupational infections amenable to specific control interventions. Geographic or temporal clusters of cases or clustering among persons with similar attributes or occupational tasks suggest a common source of exposure and infection and warrant investigation. Local public health officials and regulatory agencies should be consulted promptly when an outbreak is initially suspected. Reporting of occupationally acquired infections permits public health agencies to identify clusters of old and emerging illnesses and ultimately prevent them. These events should be reported as mandated by state and local regulations. 48, 49 Return-to-work criteria Employees diagnosed with communicable infectious diseases should not return to work until the period of infectivity is past. Specific guidelines should be consistent with local public health regulations. Some workers, for example food handlers with certain diarrheal illnesses, cannot resume their duties until culture evidence of cure is obtained. Employees should be advised of the return-towork policies at the time of employment and when illness is diagnosed. A table for length of work restriction for healthcare personnel can be used to guide return-to-work policies for the workplace (Table 22. 2). 19

Common sense dictates attention to personal hygiene among all workers. Hand washing after using the bathroom and before handling food is essential. The mouth should be covered while sneezing or coughing, and soiled tissues and dressings should be disposed of in trash containers.

Employers have a responsibility to minimize crowding in the work setting. Facilities for hand washing should be available in bathrooms and food preparation areas. Proper ventilation also is important. Trash should be emptied at regular intervals, and work areas should be clean and free of pests.

Smoking should be prohibited in common work areas.

Spills of blood, body fluids, and other potentially infectious substances should be removed with disposable paper towels or other suitable procedures. Contaminated areas should then be disinfected with commercial products or with a solution of household bleach (diluted 1:100). 34, 36 Infection control in healthcare settings Infection control programs in healthcare settings are necessary to prevent transmission of healthcare-related infections to patients and healthcare personnel. The CDC has established a two-tiered system of infection control precautions. 16 The first tier consists of 'standard precautions' which are precautions recommended for delivery of care to all patients regardless of diagnosis or presumed infection status. They are designed to limit exposure to blood or other body substances and include elements such as hand hygiene and use of appropriate protective barriers, e.g., masks, eye protection, and gloves, as needed to prevent direct contact. The second tier of precautions recommended by CDC are 'transmission-based precautions', designed for the management of patients known or suspected to be infected with pathogens whose transmission can be limited by the adoption of additional measures beyond those which are part of standard precautions. They apply to pathogens transmitted by the air-borne or aerosol routes, droplets, and by direct and indirect contact.

Respiratory precautions are employed for patients with infections communicable by the air-borne route. Such patients are housed in private rooms with special ventilation and should wear surgical masks when leaving their rooms. Respiratory protection (i.e., N-95 respirators) also are advised for providers in close contact with patients on respiratory precautions. However, the re-emergence of epidemic and MDR-TB has led to a re-emphasis of other fundamentals for prevention of transmission of tuberculosis in healthcare and other settings. Early identification of TB allows early indication for therapy, and requires alertness in considering TB in high-risk patients with pulmonary symptoms, especially those with HIV infection. Special ventilation measures and respiratory protection are especially important for cough-inducing procedures, such as sputum induction and aerosolized pentamidine administration. Healthcare personnel who have the potential for being exposed to M. tuberculosis should be screened on employment and at least annually thereafter by PPD skin testing, comparing previous test results to current results to identify those who have converted to skin test positivity. 15 Procedures for disposal of infectious wastes have been developed by the CDC. 36 Needles and other sharp objects should be sterilized prior to disposal. Liquid and laboratory wastes may be dumped into sewage systems. Materials heavily contaminated with bacteria or blood should be placed in special bags that are specifically labeled for infectious waste and should be disposed of according to community standards for such materials. 36 Employers have a responsibility to educate employees about infection control. Barriers to prevent exposure, including masks, gowns, eye protection, and gloves, should be readily available to workers at risk. Hand washing facilities and hand hygiene supplies are essential. Where access to sinks or running water is not feasible, alcohol hand rubs or packaged towels containing disinfectants should be provided.

Impervious containers for the disposal of needles and other sharp objects are essential. 50 Such containers should be made available on ambulances and provided to home health aides and other visiting healthcare personnel. Personal service workers who use needles, razors, and other sharp objects also should have access to safe disposal units. Persons receiving care at home who require injections or other procedures that demand the use of needles also should be provided with impervious disposal containers and instructed in proper disposal methods to protect sanitation workers and others in contact with waste.

Despite improvements in engineering controls, work practices, and personal protective equipment, laboratory personnel are nevertheless at risk for occupationally acquired infections. Laboratory personnel may acquire infection by aerosolization of specimens, mouth pipetting, or percutaneous injury or mucocutaneous contact. Methods of infection control applicable to laboratory settings are described in the CDC document entitled 'Biosafety in Microbiological and Biomedical Laboratories'. 47

By 1995, it was estimated that 14.5 million children were attending out-of-home daycare in a variety of settings including licensed child daycare centers, regulated daycare homes, and unregulated family daycare homes. 51 Many serious infections occur as endemic or microepidemic problems in the daycare setting. These include H. influenzae type b, hepatitis A, cytomegalovirus, parvovirus B 19, and enteric infections (Shigella, Giardia, rotavirus, Clostridium difficile, Campylobacter, Cryptosporidium, calcivirus, Salmonella, enteric adenovirus, astrovirus, and several types of E. coli infections). In addition, the high rate of acute respiratory infections leads to early onset of otitis media, frequent antibiotic use, and emergence of multidrug-resistant enteric pathogens.

Thus, workers in close contact with children risk exposure to a wide variety of communicable pathogens contained in secretions, urine, and stool. All such personnel, as well as all children in schools and daycare centers, should be screened for immunity to common childhood infections and vaccinated if immunity is not present (Table 22. 2).

Regulation of childcare facilities is essential to reduce risks to children and workers. National standards for infection control in childcare facilities were promulgated in 1990. 52 Hand washing facilities and policies are the most important component of disease prevention in school and daycare settings. Hands should be washed after contact with mucous membranes and potentially infected body fluids. Older children should be instructed in personal hygiene. Children with fever or diagnosed infections should be excluded from attending daycare or school until transmission risk is no longer present, and policies for such exclusion should be in place. Prompt reporting of disease outbreaks and prompt involvement of public health authorities are essential. Employees should be instructed in common-sense first aid procedures for handling wounds, bites, and other situations in which exposure to infected blood or tissues is possible. Barrier protection is rarely required in schools, but gloves should generally be available for emergencies requiring first aid.

Infection with a variety of agents during pregnancy has the potential to cause fetal damage, especially when primary infection occurs. While a number of these infections can be community acquired, the likelihood of exposure to certain of these pathogens can be greater in healthcare settings. Infections with as rubella, CMV, and parvovirus are among the infectious agents which may be of special concern to pregnant healthcare personnel. In general, adherence to standard precautions as well as preexposure immunizations when available and appropriate are the best way of preventing the devastating effects of such infections (Table 22. 2). 19, 21 

Immunodeficient workers are at increased risk of devastating infections, particularly with opportunistic agents. The greatest risk for such workers is likely in the healthcare setting where there can be ample opportunity for exposure to these agents. Many immunocompromising illnesses would be viewed by the US legal system as disabilities and therefore, individuals with those conditions would be covered under the provisions of the Americans with Disabilities Act of 1990 (see Chapter 57.1). 53 Such persons should be informed about their risks and furthermore, their employers should make reasonable accommodations to allow their employees to continue to perform their jobs, taking into consideration the provisions of applicable federal, state, and local regulations.

Occupational infectious diseases encompass a large variety of infections which can involve many organ systems. They include some common infections, such as influenza, that pose a special problem in the workplace because of close interpersonal contact and crowding, and that taken together account for a large proportion of time lost from work. Many of these infections are preventable by policies that promote hygiene and provide exclusion from work during periods of contagion. In addition, a variety of less common, but sometimes serious, infections are particularly associated with specific occupations. Recognition of the types of infection risk associated with specific occupations can, in most cases, lead to effective, often simple steps for primary prevention, as well as opportunities for early diagnosis and treatment.

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Known responder ¶ Known non-responder** Antibody response unknown HBIG § × 1 and initiate hepatitis B vaccine series No treatment HBIG x 1 and initiate revaccination or HBIG × 2 † † Test exposed person for anti-HBs: § § If drug resistance is a concern, obtain expert consultation. Initiation of postexposure prophylaxis (PEP) should not be delayed pending expert consultation, and, because expert consultation alone cannot substitute for face-to-face counseling, resources should be available to provide immediate evaluation and follow-up care for all exposures. § Source of unknown HIV status (e.g., deceased source person with no samples available for HIV testing). ¶ Unknown source (e.g., splash from inappropriately disposed blood). ** Small volume (i.e., a few drops). † † The designation 'consider PEP' indicates that PEP is optional and should be based on an individualized decision between the exposed person and the treating clinician. § § If PEP is offered and taken, and the source is later determined to be HIV negative, PEP should be discontinued. ¶ ¶ Large volume (i.e., major blood splash).