A case-control study of acute hepatitis A in South Korea, 2019.

OBJECTIVES

We aimed to reconfirm the source of hepatitis A virus (HAV) infection through epidemiological and genotype investigations of individual cases in a 2019 outbreak in South Korea.

METHODS

We investigated food intake histories, associations with hepatitis A, and genotypes of HAV in 31 patients with hepatitis aged 20 to 49 years registered in the integrated disease and health management system during December 1-7, 2019 (case group) and in 35 sex- and agematched people without a history of HAV vaccination or infection among patients' families and colleagues (control group).

RESULTS

The consumption of salted clams was a significant factor (odds ratio, 4.33; 95% confidence interval, 1.32-14.18) in the risk factor analysis of food intake history. HAV genotypes were analyzed in 24 of 31 patients. Type IA and type IIIA were found in 23 and 1 cases, respectively.

CONCLUSION

Salted clams are considered to have been the source of HAV infection at 49 weeks of the HAV outbreak in 2019; this result was consistent with that of a previous epidemiological investigation conducted by the Korea Disease Control and Prevention Agency in September 2019. Therefore, monitoring of the production and distribution of salted clams needs to be continued.