JLE

Virologie

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Viral enteric risk in 1998 Volume 2, issue 2, Mars-Avril 1998

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Most 150 viral genus transmitted by fecal-oral route are involved in severe morbidity and high mortality by diarrhea, poliomyelitis and acute hepatitis. These viruses are closely linked to transmission course including humans, animals, water sources. Resistance to environmental factors, physical and biochemical inactivation contributes to the spread of infection. The contamination risk depends on virus amount in the feces (as high as 10 10 per gram for rotavirus and 10 9 per gram for HAV), the pattern of fecal excretion, ranging from 10 days for rotavirus to 2-3 weeks for HAV, HEV and socio-economic status. They are detected in raw sewage and survive in wastewater sludges although treatment processes can reduce concentration of viruses. The enteric risk is associated with a low infectious dose as 10-100 particles/ml. The main modes of contamination are from person to person for rotavirus, Norwalk group virus, enterovirus, enteric adenovirus and HAV. The consumption of polluated drinking water or contaminated food has been documented as source of outbreaks of hepatitis A and E and Norwalk gastroenteritis. Diagnosis requires detection of virus or viral antigen and/or demonstration of a serologic response. Detection virus in stools is limited. IEM continues to be useful for identification of 27-30 nm virus-like particles, coronaviruses and parvoviruses. Elisa tests for detection of most viral antigens in stool samples have been developed. Latex agglutination tests are only available for Group A rotaviruses and enteric adenoviruses. PCR techniques can detect viruses in feces but fail to evaluate viral infectivity. Antibody Elisa systems enable epidemiological studies, especially related to Norwalk group viruses, enteroviruses, astroviruses. Serological assays contribute to diagnosis of acute infections as hepatitis A and E. Viral surveillance of waste water should be a criteria to control enteric risk and evaluate inapparent discharge within the community. Although prevalence rate and morbidity depend on socio-economic status, enteric risk has a worldwide distribution. Current strategies to prevent enterically transmitted infections are improvement in hygienic and sanitary practices and immunizations. Effective poliomyelitis and hepatitis A vaccines are recommended. The first generation of rotavirus vaccines to be licensed should be the rhesus tetravalent rotavirus vaccine. Nevertheless, enteric risk will be efficiently collapsed by hygiene, health education, sanitation and drinking water supplies. It results in development.