Acute haemorrhagic conjunctivitis: seroepidemiology of coxsackievirus A24 variant and enterovirus 70 in Singapore.

Epidemics of acute haemorrhagic conjunctivitis caused by a variant of coxsackievirus A24 (CA24v) and enterovirus 70 (EV70) have occurred periodically in Singapore. A seroepidemiological survey conducted before the CA24v epidemic in 1985 and in the midst of the EV70 epidemic in 1983 showed a neutralising antibody prevalence (greater than or equal to 1:4) of 19.1% and 66.9% to CA24v and EV70, respectively. The seropositivity rate to both viruses was highest in children 10-14 years of age, but no sex or ethnic difference was noted. It appears from the data that an epidemic could be triggered when the herd immunity of the population falls below a critical level. There was a significant correlation in seroprevalence between CA24v and EV70 (P = 7.75 x 10(-3).