The investigation of a recurrence of an AHC virus epidemic at Lucknow: a serosurvey for AHC virus antibodies before and after the epidemic.

An epidemic of acute haemorrhagic conjunctivitis (AHC) recurred at Lucknow during July to September 1975, after a gap of 4 years. Out of the 35 cases investigated thoroughly, 20 Entero-70-like cytopathogenic agents were isolated from the conjunctiva which were neutralized by antisera against AHC virus J670/71 of Japan. Seroconversion was seen in 7 out of 11 paired sera from patients. Serological study was also done on 100 sera collected before the AHC epidemic of 1971, 100 sera after 1971 and 100 sera after 1975 epidemic. There were no neutralizing antibodies in the pre-epidemic period, while 18% of sera after the first epidemic and 32% after the second epidemic showed antibodies. The incidence of antibodies was highest (43%) in children aged below 10 years. Of the children born after the first epidemic, 44% had antibodies. Thus our findings show that the AHC virus appeared for the firt time at Lucknow in 1971 and the almost complete absence of disease in children, and its mildness during second epidemic, may be due to immunity.