Seroepidemiology of a second epidemic of hepatitis E in a population that had recorded first epidemic 30 years before and has been under surveillance since then.

PURPOSE: Large-scale waterborne epidemics of hepatitis E occur in developing countries. It is not known why these epidemics occur repeatedly and selectively in adult population?
METHODS: We studied seroepidemiology of an outbreak of hepatitis E in one of 15 villages that had recorded first epidemic of hepatitis E 30 years back. Another village not affected by the second epidemic was taken as a control. Overall, 1,216 sera were collected (638 from the epidemic village and 578 from the control village) for serological markers of both hepatitis A virus (HAV) and hepatitis E virus (HEV).
RESULTS: The seroprevalence of anti-HEV in this population following the first epidemic in 1978 was 29.4%. Antibodies were detected in only 47% of the 45 patients affected by icteric HEV infection 14 years after the first epidemic. At 30-year follow-up, the seroprevalence of anti-HEV was only 4.5% (26/578). In the village affected by second epidemic, 138 (21.6%) subjects had serological evidence of recent HEV infection. The attack rate was 23.6% (78/330) in children (≤14 years) and 19.4% (60/308) in adults (P = 0.21). The attack rate of anicteric HEV infection was 21.8% (72/330) in children and 14.6% (45/308) in adults (P = 0.02).
CONCLUSIONS: Following hepatitis E epidemics, there is a gradual loss of antibodies in the community over the decades and poor exposure to HEV infection in the cohort of population born during the interepidemic period. The next epidemic occurs when antibody levels fall to critically low levels and there is associated gross fecal contamination of water resources. During epidemic, persons of all age groups are exposed to infection, with predominant anicteric disease in children.