Implications of recent virological researches.

Rotaviruses (duoviruses) can be found in more than half the cases of acute diarrhoea in children up to the age of six or seven. About that age almost everyone has antibodies to them. Second infections occur and may not be as rare as laboratory findings so far suggest. Very young infants sometimes get subclinical disease-the effect of maternal antibody transmitted across the placenta? Very similar viruses, all possessing a common antigen detectable by immunofluorescence, are known to infect and/or cause diarrhoea in children, calves, piglets, mice, foals and monkeys. The calf virus and the human virus both infect piglets; piglet virus infects calves; we don't know whether any of these can infect children. Other mammals probably have similar diarrhoea viruses. An antigen common to all these viruses is probably in the inner capsid layer, and "species-specific" antigens are probably in the outer capsid layer. A precise test for comparing different strains is bably needed. Adenoviruses possibly cause a smaller proportion of cases of diarrhoea. Coronaviruses, well-known as enteric pathogens of pigs and calves, appear also to infect adults and children. 27 nm particles and 22-23 nm particles of density 1.4 (and other particles) can be found in faeces of children with natural diarrhoea and adults with experimental diarrhoea, sometimes in enormous numbers. It is not yet established whether they cause disease. Rotaviruses, animal coronaviruses and "Norwalk" virus attack the disaccharidase-producing epithelium of the small bowel; adenovirus pathology is unknown.A safe attenuated live vaccine strain of the human rotavirus urgently needs to be developed.