Novel rotaviruses in animals and man.

Novel (non-group A) rotaviruses have many of the morphological, biochemical and biological properties described originally for group A rotaviruses but they do not share the same group antigens. By negative-stain electron microscopy, novel rotaviruses have the characteristic rotavirus morphology, although with some novel rotaviruses the characteristic single- and double-shelled particles may not be readily apparent. Comparison of novel rotaviruses in serological tests has revealed the existence of at least six rotavirus serogroups, A to F, with the original rotaviruses belonging to group A. As with group A rotaviruses, viruses from different animal species, including man, can belong to the same serogroup. A further point of difference between novel and group A rotaviruses is their genome profiles, which lack the triplet of segments in the 7-8-9 region of group A rotaviruses. This is a useful diagnostic aid. Novel rotaviruses have been found in farm animals and man. They can cause enteritis experimentally and infect villus enterocytes. In chickens, turkeys, lambs and pigs the viruses and/or antibody to them are commonly found, in association with either clinical or subclinical infection. In humans one type of novel virus has emerged as a cause of severe diarrhoeal disease in adults. The possible reasons for the relatively recent discovery of the novel rotaviruses are discussed.