Background: Improvement of hygiene and vaccination reduce the risk of hepatitis A virus (HAV) in Asia, however outbreaks of hepatitis A are still common. On June 29, 2022, an acute jaundice case was reported at an Islamic Boarding School, in Kebumen district, Indonesia. An epidemiological investigation was conducted to confirm the event, identify the risk factors, and provide recommendations to control the outbreak.

Methods: We conducted a 1:2 case-control study. Confirmed cases were students with one or more symptoms of fever, headache, dark urine, nausea, or jaundice and positive for HAV or have an epidemiological link with confirmed HAV case(s), from June to August 2022. Controls were students from the same boarding school with no above mentioned symptoms. One serum sample from a symptomatic student was collected for HAV-testing. Six drinking water sources and cafetaria were tested for water quality. Residents were interviewed for risk factors. Logistic regression calculated adjusted odds ratios (AOR).

Results: There were 47 confirmed cases among 232 residents. Majority of cases (53%) were females, age 12-17 years. Students under 15 years old had the highest attack rate (28%). Thirty-seven (79%) cases had fever, 32 (68%) had headaches, 24 (51%) had dark urine, and 16 (34%) developed jaundice. The serum sample was positive for HAV. No cases had a hepatitis A vaccination. All six water samples had fecal coliform counts above the standard. Eating together on the same plate (kembulan) was the risk factor related to cases (AOR=4.1; 95% CI 1.4– 11.7).

Conclusions: An outbreak of HAV occurred among students in an Islamic Boarding School. We suspected non-potable drinking water sources and eating together on the same plate as risk factors for this outbreak. Our recommendations for controlling future outbreaks are promoting hygiene sanitation practices and HAV vaccination.