Role of travel as a risk factor for hepatitis E virus infection in a disease-endemic area

We undertook epidemiologic and laboratory studies during an epidemic of acute hepatitis in Sindri town, in District Dhanbad, Bihar in 1998.A sample survey covering 201 randomly selected houses in the town was conducted during the epidemic, and records of patients admitted to the only large hospital in this town were reviewed. We also tested serum and stool specimens from some of the affected persons for hepatitis E virus (HEV) RNA and IgM anti-HEV antibodies.Of the 1088 persons residing in the surveyed houses, 82 (7.54%) had developed acute hepatitis during the outbreak. Attack rate was higher among male residents than among female residents (71/604 vs. 11/484; 11.75% vs. 2.27%; relative risk [RR] 5.17 [95% confidence interval 2.77-9.65]; p10(-6)) and was the highest in the 10-29 year age group. Hospital admission data showed similar age and gender distribution. Disease occurrence had no relation with source of drinking water (handpump 7.56% vs. municipal tap 7.53%; p=ns), or with habit of boiling (RR 1.10 [0.61-1.98]; p=ns) or filtering (RR 0.59 [0.33-1.06]; p=ns) water before drinking. Jaundice occurred more frequently among persons who had traveled outside Sindri town during the last two months than among those who had not (26.4% vs. 4.7%; RR 5.67 [3.81-8.43]; p10(-6)); this risk persisted after correction for age (Mantel-Haenszel weighted OR 6.74 [4.12-11.01]; p10(-6)). Men traveled more frequently than women and were more often affected. In multivariate analysis, travel and male gender were the only two independent risk factors. Data from a hospital in a neighboring large city, Dhanbad, suggested that there was an outbreak of hepatitis in that city too at the same time. Seventy-three of the 1088 study subjects had history of jaundice in the past; disease attack rate among these persons (9.6%) was similar to that among those without such history (7.5%; RR 1.31 [0.49-2.98]; p=ns). Of the 13 sera tested, 10 were positive for IgM anti-HEV. HEV RNA was detected in 9 of the 12 stool specimens and 10 of the 13 sera tested.The hepatitis epidemic in Sindri was caused by HEV and had several features resembling those of previous HEV epidemics. However, the occurrence of hepatitis E showed a strong relationship with history of travel, a finding not hitherto described.