What is already known about this topic? Hepatitis A (HA) is caused by acute hepatitis A virus (HAV) infection and was once very common in China. Following the 2008 introduction of the HA vaccine into the national Expanded Program on Immunization (EPI), the incidence of reported HA in China decreased markedly. However, HA epidemics still occur in Liaoning Province every 3-5 years, although with far fewer cases than in the pre-HA-vaccination era. What is added by this report? Between January 1, 2020 and March 18, 2020, the number of reported cases of HA in Dalian and Dandong cities of Liaoning Province increased significantly compared with the same period in previous years. All cases were sporadic, and cases were seen in nearly every township. The increase in HA occurred one month after local fresh seafood became available with most cases being among adults. A case-control study showed that consuming raw or undercooked seafood, clams, snapping shrimp, and oysters were significantly associated with the increase in HA. What are the implications for public health practices? Strengthening health education for residents to avoid consumption of raw seafood and encouraging HAV vaccination of adults aged 20 to 54 years are important to prevent periodic HAV endemic outbreaks. Further multisectoral cooperation must be emphasized on HA surveillance in areas with a high prevalence of HA.