key: cord-0009237-vetrb61q authors: Gray, Larry D. title: Novel viruses associated with gastroenteritis date: 1991-09-15 journal: Clin Microbiol Newsl DOI: 10.1016/0196-4399(91)90041-s sha: e8519f0bc04b01f237d4093cbb7e82ebceb0f8eb doc_id: 9237 cord_uid: vetrb61q nan ). Many of these novel viruses have several characteristics in common: (i) small size, simple structure, and EM and physical characteristics; (ii) fastidious nature (inability to be cultured routinely); (iii) ability to elicit severe diarrhea that is easily alleviated by fluid and electrolyte replacement; and (iv) previously recognized and well known abilities to cause gastroenteritis in animals. The following are brief descriptions of two well recognized and several novel viruses associated with gastroenteritis. References 1 through 8 are excellent sources of additional information on these viruses. Rotavirus is a 70-nm, nonenveloped, 1 l-segment double-stranded (ds) RNA virus with two icosahedral capsids. It infects humans and most species of animals. Rotaviruses are members of the family Reoviridae and are named as such because of their wheellike appearance when observed by EM. Typical rotaviruses are intimately associated with severe gastroenteritis worldwide in the very young of all susceptible host species. The most commonly affected humans are children age 6 mo to 2 yr old. Until 1982, rotaviruses were thought to be comprised of only one antigenic group (group A or "typical" rotaviruses) which is defined by the group antigen associated with the inner capsid and which causes diarrhea predom- Novel Gastroenteritis Viruses .... 137 Recently discovered viruses responsible for epidemic and endemic gastroenteritis inantly in neonates and young children. In 1982, rotavirus group B was recognized as a human pathogen when it caused epidemics of gastroenteritis in China (9) . An interesting observation in the Chinese epidemics was the more common occurrence of illness in adults rather than in young children. Rotavirus group B has been detected sporadically in Australia, Brazil, and the U.S., and there is serological evidence that rotavirus group B has infected people in Southeast Asia (1) . However, significant rotavirus group B gastroenteritis has not occurred outside of China. Because rotavirus group B is a common diarrheal pathogen in swine, and has a segmented genome similar to that of influenza viruses (and is even grouped alphabetically like influenza viruses), phenotypic changes due to reassortment of the swine rotavirus group B genome could (or perhaps can in the future) have facilitated the ability of the swine virus to infect humans (1) . Rotavirus group C is primarily a swine virus but has been detected in humans in the U.S. and other areas of the world, particularly England, Japan, Australia, and Brazil (1, 4, 10) . In the U.S., serological evidence suggests that exposure to rotavirus groups B and C has been minimal. Rotavirus groups D, E, and F have been found only in animals. Rotavirus has been cultured in vitro in CV-1, LLC-MK2, AGMK, PCMK, and MA-I04 cells. However, culture is not commonly performed in clinical microbiology laboratories because culture of rotavirus often requires special procedures such as previous passage in fetal or gnotobiotic cell lines, pretreatment of specimens with trypsin, or the addition of trypsin to maintenance media. In addition, cytopathic effect is not consistently present or reproducible (4) . Historically, rotavirus has been de-tected directly in stool specimens by EM. Specimens can be homogenized and diluted, negatively stained with phosphotungstic acid, and examined. Two reasons that this relatively simple and sensitive (albeit expensive) technique is still considered by some workers to be the standard method for detecting rotavirus are the large amount of virus shed in stools and the often relatively bacteria-free (clean) state of rotavirus-elicited stools. The EM technique requires the presence of > 106 virus particles/g feces for optimum sensitivity. In a technique known as immune electron microscopy (IEM), convalescent antirotavirus serum can be mixed with rotavirus purified from specimens and examined by EM. The resulting aggregates of virus are usually easily observed and exclude irrelevant particles with morphology similar to that of rotavirus. In addition, the method can provide information as to the serotype of the virus. Some workers have coated EM grids with Staphylococcus aureus protein A, adsorbed rotavirus-specific antiserum to the protein, and used these grids to serotype rotavirus (11, 121. Enzyme immunoassay (EIA) and latex agglutination (LA) are more commonly used to detect rotavirus in stools than is EM because the former methods are considerably less expensive and labor-intensive, and do not require special equipment. EIA is probably at least as sensitive as EM. In addition, the large amount of antigen in rotavirus-elicited stools is usually ample for detection. Several commercial rotavirus E1A (both monoclonal and polyclonal antibody-based) and LA kits are available. The literature is replete with interproduct comparisons as well as comparisons of products with EM (4, 13, 14) . Reported sensitivities and specificities of EIA kits range from 50 to 100% and from 71 to 98%, respectively. Re-ported sensitivities and specilicitic,, ot LA kits range from 61 to 96+~ and from 72 to 100c~, respectively. Scnsv tivities and specificities appear to depend on the studied patient population (both are highest in neonatest and on the standards to which the products arc compared (EM or other kits). Hemagglutination, counterimmunoelectrophoresis, immunofluorescence, complement fixation, and radioimlnunoassay also have been used to detect rotavirus antigens; however, these methods are not widely accepted because they are relatively insensitive, may require radiolabeled reagents, or are not practical for other reasons. Several methods to detect antirotavims IgG, IgM, and lgA have been described but these are not useful in the diagnosis of rotavirus infection and, therefore, are not commercially available. Adenovirus is a 70-nm, nonenveloped single-segment ds DNA virus with an icosahedral capsid which has a single fiber/spike at each vertex. Serological specificity is determined by the protein antigens of the capsid. All mammalian adenoviruses have a common antigen that can be easily detected by complement fixation. Adenoviruses are typed according to their serological specificities 141 known serotypes/species), protein composition (groups A through F), and nucleic acid restriction endonuclease patterns (groups A through G). In general, serotypes I-3 and 5-39, 4, 40, and 41 correspond to groups A-D, E, F, and G, respectively. For many years, adenovirus has been cultured from and has been observed by EM in stools from healthy individuals and from patients with gastroenteritis. However, an association between adenovirus and gastroenteritis has been made only over the last 15 NOTE. No responsibility is assumed by the Publisher for any injury andJor damage to persons or property as a matter of products liability negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. No suggested test or procedure should be carried out unless, in the reader's judgment, its risk is justified. Because of rapid advances in the medical sciences, we recommend that the independent verification of diagnoses and drug dosages should be made. Discussions. views and recommendations as to medical procedures, choice of drugs and drug dosages are the responsibility of the authors. yr. During this time, "enteric" or "fastidious" (nonculturable except under special conditions) adenovirus types 40 and 41 and culturable type 31 have been found in patients with diarrhea significantly more often than in healthy individuals. Now, adenovirus types 31, 40, and 41 are recognized as occurring worldwide and as significant causes of diarrhea in children <~2 yr old (1, 4, 15) . Electron microscopy, EIA, nucleic acid probe hybridization, and special cell culture techniques have been used to detect adenovirus types 40 and 41. An EIA kit for adenovirus types 40 and 41 (Adenoclone-type 40/41; Cambridge BioScience, Worcester, Mass.) is available commercially. Adenovirus types 40 and 41 have been cultured in HeLa cells, conjunctival cells, and specially treated CMK cells (4, 16, 17) . Norwalk virus (Norwalk type virus) and Norwalklike viruses (also known as small, round, structured viruses) are 27-nm, round, and nonenveloped. The type of nucleic acid in Norwalk viruses is not known. The type virus of the group is the Norwalk virus (agent). Norwalk viruses have a simple but obvious structure that is characterized by an amorphous surface and irregular edges. Norwalk and Norwalklike viruses have similar structures, cause similar clinical gastroenteritis in older children and adults (rotavirus usually affects children <2 yr old), and are present in small numbers in diarrheal stools (rotavirus is present in large numbers). Norwalk viruses are firmly established as agents of gastroenteritis, and have caused many outbreaks of illness. Norwalk viruses have not been cultured in vitro. Physicochemical characteristics of the viruses have been determined by examining viruses partially purified from diarrheal stools. IEM has been the most commonly used method to examine stools tor Norwalk viruses, to examine the structure and antigenic relatedness of the viruses, and to determine diagnostic rises in antibody titers. EIA and RIA tests to detect Norwalk viruses have been developed and described (4, 6, 7) but are used almost exclusively for research and epidemiologic purposes. Caliciviruses are 30-nm, nonenveloped, single-stranded (ss) RNA( + ) viruses that have surface cup-shaped indentations that give the periphery of the virus a scalloped, 5-or 6-point star appearance. Calicivirus-elicited gastroenteritis is worldwide in distribution, does not occur frequently, usually affects children <5 yr old, and is not often distinguishable from that caused by rotavirus. Human calicivirus is not culturable in vitro (although animal calicivirus is readily culturable) and is usually detected in stools by EM or IEM. EIAs and RIAs have been developed to detect calicivirus and antibody to calicivirus (4, 18) . The morphology, buoyant density, structural proteins, and antigenic characteristics of calicivirus are similar enough to those of Norwalk viruses to suggest that the two may be closely related (3, 4) . Astrovirus is 30 nm in diameter, contains ss RNA( + ), and does not have an envelope. The periphery of the virus is smooth, and the surface structure appears as a 5-or 6-point star, the points of which radiate from the center of the virus. There are at least five serotypes of astrovirus and at least one group antigen. Astrovirus is associated with foodand waterborne gastroenteritis, usually affects children <7 yr old, and is not as severe as infection caused by rotavirus and Norwalk viruses (3). Astrovirus usually is shed in extraordinarily large amounts. Astrovirus has been cultured in vitro in HEK, LLC-MK2, and CaCo-2 cells (4, 7) . EM and IEM are used to detect the virus in stools and to serotype the virus, lmmunofluorescence, IEM, and E1A (both mono-and polyclonal antibody-based) have been used to detect astrovirus antigens in stools and to detect diagnostic rises in antibody titer (19) . Coronavirus contains ss RNA(+) and is round, 80 to 140 nm in diameter, and enveloped. Coronavirus is morphologically distinct because of its clublike surface projections (peplomers), the distal ends of which surround each virion and give a coronalike appearance to the particle. Coronaviruses cause many diverse diseases in animals worldwide, respiratory diseases (predominantly common colds in children), and possibly, gastroenteritis in humans. The presence of coronaviruslike particles in stools from people with gastroenteritis has been well documented by EM. However, a positive correlation between the presence of coronavirus and disease has not been demonstrated. Coronavirus is extremely difficult to culture in vitro and is often structurally distinct from classical (respiratory) coronavirus. The laboratory diagnosis of coronavirus gastroenteritis is made by EM examination of stools and/or by demonstration of a rise in antibody titer after an acute infection. Antibody concentration can be measured against only two strains (229E and OC43) but can be detected by several techniques: neutralization, complement fixation, EIA, and immunofluorescence (4, 20) . Pestivirus is ass RNA( + ) virus which is 50 nm in diameter, pleomorphic, probably icosahedral, enveloped, and difficult to identify by EM. Pestivirus is widely recognized as a cause of highly economically important diseases in animals, but has never been demonstrated in or to cause disease in humans, either directly or indirectly (21, 22) . Recently, a monoclonal antibodybased EIA was developed and used to demonstrate pestivirus antigens in 23% of the stools of children <2 yr of age with gastroenteritis that was not attributable to recognized enteric pathogens (22) . Similar methods have been used to detect pestivirus-associated gastroenteritis and pestivirus exposure in the United States, Bangladesh, and Peru (1, 2 Picobirnavirus was previously thought to cause diarrhea in animals; however, human cases of picobirnavims-associated diarrhea have been reported in Brazil (1). Parvovirns are ss DNA viruses that are 20 nm in diameter, nonenveloped, icosahedral, and not culturable in vitro. Parvoviruses are most recognized for causing numerous diseases in animals and erythema infectiosum (fifth disease) in children. However, parvovirnslike particles have been observed (by EM) in the stools of gastroenteritis patients and healthy individuals, and have been associated with shellfish-related gastroenteritis (1) . Viral agents of gastroenteritis. Public health importance and outbreak management Viral gastroenteritis Novel agents of viral enteritis in humans Human viral gastroenteritis The electron microscopical and physical characteristics of small round human fecal viruses: an interim scheme for classification Norwalk agent comes of age Viral gastroenteritis Textbook of human virology Waterborne outbreak of rotavirus diarrhoea in adults in China caused by a novel rotavirus Detection of rotavims by serological trapping on antibody-coated electron microscope grids Comparison of solid phase immune electron microscopy by use of protein A with direct electron microscopy and enzyme-linked immunosorbent assay for detection of rotavirus in stool Comparison ~l nine commercial immunoassays for the detection of mtavims in fecal specimens Evaluation of seven immunoassays for detection of rotavirus in pediatric stool samples Clinical features of adenovirus enteritis: a review of 127 cases Propagation and in vitro studies of previously non-culturable enteral adenoviruses in 293 cells Candidate adenoviruses 40 and 41: fastidious adenoviruses from human infant stool Outbreak of human calicivirus gastroenteritis in a day-care center in Sidney Diagnosis of astrovirus gastroenteritis by antigen detection with monoclonal antibodies Textbook of human virology Pestiviruses: a review Infantile gastroenteritis associated with excretion of pestivirus antigens Donald Vesley, Ph.D. Public concern over potentially hazardous solid wastes of hospital/medical origin peaked in the summer of 1988, prompted by highly publicized incidents of such wastes washing ashore on a variety of the nation's beaches.Undoubtedly, concern was fueled by the growing fear of AIDS and public inability to distinguish between genuinely infectious wastes and other items that looked bad but were only of aesthetic concern. Nationally, there was a demand for regulatory action, and the American politicians were only too anxious to respond. The federal Medical Waste Tracking Act of 1988 (Luken Bill) was passed and many, often restrictive, state laws followed. The race was on to save the nation from the "evils" of infectious waste.Hospitals and other medical facilities have been caught in a crossfire which threatens to add considerably to the already skyrocketing costs of medical care. Attempts to apply principles of logic and scientific evidence to arrive at reasonable approaches to managing medical wastes are being thwarted by extreme application of the NIMBY (not in my backyard) principle. We are left with a hodgepodge of inefficient, environmentally unsound, and sometimes outright ridiculous practices in place of sensible solutions. For example, some two-thirds of American hospitals are currently incinerating their wastes onsite. Many of these incinerators are old, inefficient,