Acute outbreaks of diarrhoea occur when the virus is first introduced into a susceptible population. The incubation period is approximately 2 days and diarrhoea lasts for 7 to 14 days. In large breeding herds, particularly if kept extensively, not all the females may become infected first time round and there may be recrudescence. This only occurs in piglets suckling from sows with no maternal antibodies and is therefore sporadic. Mortality may be high.
Mortality is usually low but morbidity can be high.
The incubation period is 2 to 4 days. The immunological status of the herd i.e. no immunity. Disease may be perpetuated as susceptible pigs enter the finishing herd. Disease normally only seen when virus first enters the herd. Post-mortem examination of dead pigs and laboratory tests on the small intestine may be necessary to confirm the diagnosis.