Hepatitis A epidemics in Japan, France, and Thailand from 2007 to 2021, highlighting a post-COVID-19 decline

Hepatitis A infection is an acute hepatitis disease transmitted through contaminated water, food, and sexual contact, especially among men who have sex with men (MSM). This retrospective cohort study analyzed trends in hepatitis A infection in Japan, France, and Thailand from 2007 to 2021 to investigate varied epidemic trends including the MSM pandemic and the COVID-19 pandemic under different public health conditions. We analyzed annual and monthly number of cases using the national surveillance databases of Japan, France, and Thailand. We statistically evaluated the decrease in hepatitis A after the COVID pandemic. Hepatitis A average incidence in Japan, France, and Thailand was 0.21, 1.79, and 0.75, respectively. Outbreaks were recorded in 2010, 2014, and 2018 for Japan, 2009 and 2017 for France, and 2012 and 2017 for Thailand. In 2012, a hepatitis A outbreak was recorded at an ice manufacturing factory in Thailand. In Japan, in 2014, 80.5% of cases were transmitted by contaminated seafood or water. Hepatitis A increased during 2017-2018 (324% in 2018 Japan, 489% in 2017 France, 166% in Thailand), possibly linked to the global MSM pandemic. After the COVID-19 pandemic, the cases significantly decreased in all three countries (p < 0.001). The characteristics of hepatitis A epidemic may reflect the activities of people, including high-risk groups.