key: cord-0036689-5x8au7f8 authors: Georgiev, Vassil St. title: Emerging and Re-emerging Infectious Diseases date: 2009 journal: National Institute of Allergy and Infectious Diseases, NIH DOI: 10.1007/978-1-60327-297-1_4 sha: 8080c6182b0f339d7ee0cbcb035217e4d7dad10e doc_id: 36689 cord_uid: 5x8au7f8 Emerging diseases include outbreaks of previously unknown diseases or known diseases whose incidence in humans has significantly increased in the past two decades. Re-emerging diseases are known diseases that have reappeared after a significant decline in incidence (http://www3.niaid.nih.gov/research/topics/emerging). Emerging diseases include outbreaks of previously unknown diseases or known diseases whose incidence in humans has significantly increased in the past two decades. Re-emerging diseases are known diseases that have reappeared after a significant decline in incidence (http://www3.niaid.nih.gov/research/topics/emerging). Within the past two decades, innovative research and improved diagnostic and detection methods have revealed a number of previously unknown human pathogens. For example, within the past decade chronic gastric ulcers, which were formerly thought to be caused by stress or diet, were found to be the result of infection by the bacterium Helicobacter pylori. New infectious diseases continue to evolve and "emerge." Changes in human demographics, behavior, land use, and so forth are contributing to the emergence of new diseases by changing transmission dynamics to bring people into closer and more frequent contact with pathogens. This may involve exposure to animal or arthropod carriers of disease. As a result of innovative research and improved diagnostic and detection methods, a number of previously unknown pathogens-very often through host switchinghave been identified as the causative agents of emerging and re-emerging diseases (www.niaid.nih.gov/dmid/eid/). For example, the increasing trade in exotic animals for pets and as food sources has contributed to the rise in opportunity for pathogens to jump from animal reservoirs to humans. For example, close contact with exotic rodents imported to the United States as pets was found to be the origin of the recent outbreak of monkeypox in the United States, and use of exotic civet cats for meat in China was found to be the route by which the SARS coronavirus made the transition from animal to human hosts (http://www3.niaid.nih.gov/research/topics/emerging). In addition to the continual discovery of new human pathogens, old infectious disease enemies are "re-emerging." Natural genetic variations, recombinations, and adaptations allow new strains of known pathogens to appear to which the immune system has not been previously exposed and is therefore not primed to recognize (e.g., influenza). Furthermore, human behavior plays an important role in the re-emergence of diseases. Increased and sometimes imprudent use of antimicrobial drugs and pesticides has led to the development of resistant pathogens, allowing many diseases that were formerly treatable with drugs to make a comeback (e.g., tuberculosis, malaria, nosocomial infections, and food-borne infections). Recently, decreased compliance with vaccination policy has also led the to re-emergence of diseases, such as measles and pertussis, that were previously under control. The use of deadly pathogens, such as smallpox or anthrax, as agents of bioterrorism is an increasingly acknowledged threat to the civilian population. Moreover, many important infectious diseases have never been adequately controlled on either the national or international level. Infectious diseases that have posed ongoing health problems in developing countries are re-emerging in the United States (e.g., food-and water-borne infections, dengue, West Nile virus) (http://www3.niaid.nih.gov/research/topics/emerging). Individual statistics for morbidity and mortality of emerging and re-emerging infections are difficult to determine because of their limited outbreaks. Current information on international outbreaks of infectious diseases can be obtained from WHO (http://www.who.int/csr/don/en/) and the CDC (http://www.cdc.gov/mmwr). Recent outbreaks include: r Human Metapneumovirus (hMPV). HMPV was first identified in The Netherlands in 2001 in samples from children with respiratory tract disease (1). It is a new member of the Paramyxoviridae family (subfamily Pneumovirus). Although newly discovered, hMPV is not thought to be a newly evolved virus because it was also found in Dutch blood samples dating back to the 1950s. Instead, it is believed that this pathogen has long been a common but undetected cause of many human respiratory illnesses. Moreover, it has been suggested that hMPV may be the second most common source of childhood respiratory infections after the respiratory syncytial virus (RSV), and its association with respiratory disease in adults and children has been reported in Canada, Australia, the United States, Hong Kong, Japan, and Finland. In addition, data from Hong Kong have indicated that half of the SARS patients tested during the recent outbreak were also co-infected with hMPV. (5) . Studies in which NVs were molecularly characterized have shown that numerous variants co-circulate in the community, but occasionally shifts did occur in which a single variant dominated over a wide geographic area (6) . During the period 1995-1996, a worldwide epidemic was observed (7) . The mechanism of emergence of these variants is unclear, but one hypothesis is that they represent widespread common-source events (5). r Toxoplasma gondii. Recently, several water-borne outbreaks of toxoplasmosis have been described (10) (11) (12) (13) (14) (15) . Data from Brazil and North America have indicated that unfiltered drinking water contaminated with the parasite's oocysts is the main source of infection. However, transmission of toxoplasmosis has also resulted from consumption of food or water contaminated with oocysts from cat feces or soil or by eating undercooked meat that contained oocysts (16, 17) . In Latin America, seroprevalence of immunoglobulin G (IgG) to T. gondii was found to be generally high, ranging from 51% to 72% (17). In response to the threat of emerging and re-emerging infectious diseases, NIAID has developed a strategy for addressing these issues through targeted research and training, initially outlined in 1999 in "A Research Agenda for Emerging Infectious Diseases" (http://www.niaid.nih.gov/ publications/execsum/bookcover.htm), later updated in 2000 as "NIAID: Planning For the 21st Century" (http:// www.niaid.nih.gov/strategicplan/pdf/splan.pdf), and in 2001 as "NIAID Global Health Research Plan for HIV/AIDS, Malaria, and Tuberculosis" (http://www.niaid.nih.gov/ publications/globalhealth/global.pdf). This document outlines the institute's plans for the next decade for diagnosing, treating, and preventing these three infections and also lays out a plan for enhancing research capacity in-country (http://www3. niaid.nih.gov/research/topics/emerging). NIAID is planning and has established several facilities and research programs to enhance research on emerging infectious diseases, including both naturally occurring outbreaks and those that may emerge as a result of deliberate release (acts of bioterrorism): This network expands the NIAID capacity to conduct clinical research studies of food-and water-borne enteric pathogens. A newly discovered human pneumovirus isolated from young children with respiratory tract disease Tick-borne relapsing fever caused by Borrelia hermsii Reemergence of epidemic Vibrio cholerae O139 Foodborne viruses Early identification of common-source foodborne virus outbreaks in Europe Molecular epidemiology of human enteric caliciviruses in The Netherlands Identification of a distinct common strain of "Norwalk-Like Viruses" having a global distribution WHO Report: Epidemic and Pandemic Alert and Response (EPR) Genotyping of chikungunya virus isolates from India during 1963-2000 by reverse transcription-polymerase chain reaction Waterborne toxoplasmosis, Northeastern Brazil Waterborne toxoplasmosis, Brazil, from field to gene Highly endemic, waterborne toxoplasmosis in North Rio de Janeiro State Potential contamination of drinking water with Toxoplasma gondii oocysts and the British Columbia Toxoplasma Investigation Team (1997) Outbreak of toxoplasmosis associated with municipal drinking water Computer-generated dot maps as an epidemiologic tool: investigating an outbreak of toxoplasmosis Toxoplasma gondii: from animals to humans r Antimicrobial research, as related to engineered threats r Innate immunity, defined as the study of nonadaptive immune mechanisms that recognize, and respond to, microorganisms, microbial products, and antigens