Suspected spread of hepatitis A virus from a restaurant among adults in rural area of the Kerala state, India.

India is experiencing a substantial decrease in early childhood exposure to hepatitis A virus (HAV). Kerala has experienced several hepatitis A outbreaks in young adults/adults in the recent past. The current hepatitis outbreak occurred in Nellikuzhi, Kerala state, India in December 2016. Investigation was carried by preparing a line list of suspected hepatitis cases. The blood and stool samples collected from patients were tested for anti-HAV/anti-Hepatitis E virus (HEV) immunoglobulin (IgM) antibodies and RNA respectively. A total of 562 suspected hepatitis cases were reported during the outbreak. Along with the first case (35 years, male), 86.1% (484/562) of the cases gave history of consuming food/water/cold drinks from one restaurant. Anti-HAV IgM positivity was 74.5% (73/98) in tested samples and amongst the positives, 81% were adults/young adults and adolescents. None of the samples tested positive for anti-HEV IgM. There were three HAV associated deaths without any co-morbidity. Sequence analysis of HAV RNA positive stool samples showed the presence of genotype IIIA HAV. The suspected source of the infection was a private well situated in the premise of a restaurant. Considering increasing HAV naive population in Kerala, there is a need to introduce hepatitis A vaccine in high-risk age groups.