Epidemiological and genetic analysis of a sustained community-wide outbreak of hepatitis A in the Republic of Korea, 2008: A hospital-based case–control study

BackgroundThe epidemiological shift of hepatitis A has contributed to a sustained community-wide outbreak in Korea during 2008.ObjectivesTo assess the risk factors associated with hepatitis A virus (HAV) propagation, and to analyze the circulating genotype in the sustained community-wide outbreak.Study designThe hospital-based case–control study was conducted in an 850-bed university hospital in Seoul from April to August, 2008. For molecular analysis of HAV isolates, a 488-bp gene fragment of the VP1 region was amplified and sequenced.ResultsIn the multivariated logistic regression model, the risk factors of HAV infection adjusted by age were contacts with hepatitis A case (OR 3.98, 95% CI: 1.36–11.66), residence with child aged ≤5 years (OR 3.43, 95% CI: 1.32–8.87), consuming uncooked lettuce (OR 3.98, 95% CI: 1.83–8.68) or carrot (OR 2.38, 95% CI: 2.38–5.09), drinking tap water (OR 3.68, 95% CI: 1.62–8.37) or portable spring water (OR 2.71, 95% CI: 1.11–6.62) supplied by water purifiers, and eating out (OR 3.87, 95% CI: 1.53–9.78). All isolates analyzed belonged to genotype IIIA. There were 42 nucleotide differences in the sequenced VP1 region among the isolates. Amino acid sequences were identical with each other.ConclusionsOur study suggests that sporadically contaminated food- or water-borne sources as well as person-to-person transmission might lead a sustained community-wide HAV outbreak and pre-existing dominant genotype IA might be replaced with genotype IIIA as a major epidemic strain in Korea. Our findings urge the health authority to make public guidelines for HAV vaccination and outbreak control.