Investigation of an epidemic of Hepatitis E in Nellore in south India

OBJECTIVE To determine the incidence of acute hepatitis because of hepatitis E virus (HEV) and the source of the epidemic in Nellore in south India in 2008. METHODS Anti-HEV IgM ELISA and RT-PCR for HEV-RNA were carried out on blood and stool samples from patients with acute hepatitis presenting to different hospitals in the city. The city was divided into 33 clusters, and 20 families from each cluster were systematically interviewed to determine the incidence of hepatitis E in the city. The survey was conducted on 2685 residents of 673 households from 24th November to 4th December 2008. RESULTS The overall incidence of hepatitis was 5.7% (152/2685), i.e. an estimated 23 915 persons in the city were affected. There were two deaths because of acute hepatitis in the population surveyed translating to an estimated 315 deaths. Men had higher attack rates than women (7.8% vs. 3.5%) and young adults compared to children under 5 years (6.9% vs. 2.9%). Families drinking water from the pumping station at Bujjamarevu had the highest attack rate of 54.5% (39.8-69.2%). HEV IgM antibodies were present in 80/100 plasma samples tested. HEV-RNA was detected in 43/100 individuals tested, and isolates were characterized as genotype 1 by sequencing. CONCLUSION Sewage draining into the river close to the pumping stations and broken pipelines crossing sewage drains may have triggered this large outbreak.