Viruses in Faeces

Such viruses as enteroviruses (hepatitis A may now be included in this group), rotaviruses, parvovirus-like viruses, astroviruses, caliciviruses, adenoviruses and coronaviruses may be detected in human faecal extracts. Although acute poliomyelitis is seldom accounted in developed countries, which now administer polio vaccines routinely to children, poliomyelitis is a still a considerable problem in many developing countries. In parts of India, about 3.4/1000 children have poliovirus induced deformities, infection occurring most commonly in infancy. In temperate climates, outbreaks of echovirus infection occur periodically and although small children are most frequently infected, CNS involvement is reported more commonly in those aged 25-44 years. Although most persons living in developing countries acquire immunity to hepatitis A in childhood, only about 30% of healthy blood donors in the UK have immunity. Unlike infection by hepatitis B virus, hepatitis A virus does not cause post-transfusion hepatitis or outbreaks of hepatitis among haemodialysis patients. Furthermore, hepatitis A does not induce chronic liver disease. Patients with hepatitis A virus are most infectious during the latter part of the incubation period, but once symptoms develop very little virus is present in the faeces. Rotaviruses are the commonest cause of acute non-bacterial gastroenteritis in infancy and childhood. In temperate climates, infection occurs most frequently during winter months and in children aged 6 months to 3 years. Studies in hospital have shown that 40-50% of children admitted with acute diarrhoeal disease are excreting rotavirus, but in winter the proportion may be as high as 70-80%. Rotaviruses have also been shown to cause acute infantile gastroenteritis in developing countries although there is considerable variation in the incidence of rotavirus infection among children in the tropics. Parvovirus-like viruses cause winter vomiting disease and although different serotypes have been identified, approximately 25% of outbreaks appear to be related to Norwalk agent which represents the protype for this group viruses. Astroviruses and caliciviruses may induce acute diarrhoeal disease in childhood but they probably represent relatively minor pathogens. The role of coronaviruses remains to be established.