[Rotavirus and other viruses of diarrhea].

Bajolet, O; Chippaux-Hyppolite, C

Rotaviruses represent 80% of recognized viral etiologies and 140 million cases of diarrhea per year. They strike young children with similar frequency throughout the world, but the mortality rate is high in developing countries only, with some 870,000 deaths per year (WHO, 1997). Rotaviruses belong to the family of Reoviridae; they are segmented bicatenary RNA viruses, which explains their genetic variability, the presence of mixed infections, the establishment for some time already of a molecular epidemiology by electrophore types. The viruses are "naked" and thus resistant to the outside environment; their massive elimination, 10(8) to 10(10)viral particles per gram of faeces, begins with the first day of diarrhea. They are found in used water and can also be concentrated by shellfish; the environment thus constitutes a notable reservoir for the virus. Oral-faecal transmission is facilitated by deficient sanitary conditions. The 11 fragments of the genome each codify for 1 viral protein; 2 surface proteins, VP4 and VP7, bring about the formation of neutralizing antibodies, which are important for the protection and determination of different serotypes. A non structural protein--NSP4--would seem to intervene in the cytopathogenic effect and may act as a veritable viral enterotoxine. Numerous animal species are infected by rotaviruses which are district from the human ones. The pathology as it affects animals is of economic importance and of interest as an experimental and vaccinal model. Between human and animal rotaviruses there can be genetic rematchings and the VP6 protein is an antigen common to the group. The description of the other viruses responsible for diarrhea has benefited from widespread use of electronic microscopes from the very first years of study of rotaviruses. These other viruses belong to 6 different types: adenovirus, calcivirus, astrovirus, Norwalk agent and related viruses, coronavirus, enterovirus. They therefore have a structural and antigenic polymorphism but, except for the coronavirus, they are all "naked" virions with resistance in outside environments and means of transmission analogous to the rotaviruses. Clinical signs of viral gastroenterites, the age of the patient and epidemiological circumstances help in making an etiological diagnosis; the biological diagnosis has been simplified for the rotaviruses and the adenoviruses. Epidemics related to food, or of hydric and nosocomial origin, especially those due to the Norwalk agent, are under-declared and more frequent than those of bacterial origin. The prevention of dangers related to faeces, the improvement of sanitary conditions, health education, and better nutrition contribute to rotavirus prevention, but rotavirus diarrheas, the incidence of which is similar in developed and developing countries, would be more efficiently controlled through vaccination.