Hepatitis A Cluster Under Investigation in Hong Kong, Primarily Affecting Men Who Have Sex with Men
Hong Kong health officials are investigating a cluster of hepatitis A infections, with a significant proportion of cases linked to men who have sex with men (MSM). The Centre for Health Protection (CHP) of the Department of Health (DH) is urging vigilance and recommending vaccination for those at increased risk.
Cluster Details
As of March 11, 2026, the CHP has recorded 24 cases of hepatitis A infection over the past six months (September 2025 to February 2026) where the virus detected harbored an identical genetic sequence. The cases involve 22 males and two females, aged between 18 and 55. At least 14 of those infected, over 60%, have identified as MSM.
Notably, epidemiological investigations have not revealed any commonalities in the patients’ residences or the restaurants they frequent, suggesting the infection source is not linked to shared locations.
Dr. Edwin Tsui, the Controller of the CHP, stated that the CHP “cannot rule out the possibility of an epidemiological link between the infection sources of this cluster and male-male sexual contact.”
Transmission and Symptoms
Hepatitis A is primarily transmitted through the ingestion of contaminated food or water, or through contact with contaminated hands before eating. Still, the virus can as well be spread through high-risk sexual contact.
The incubation period for hepatitis A typically ranges from 14 to 28 days, but can extend up to 50 days.
Vaccination Recommendations
The CHP strongly encourages high-risk individuals, including MSM, to receive two doses of the hepatitis A vaccine. Vaccination is available and is considered the most effective way to prevent infection.
The CHP is issuing a letter to doctors reminding them to remain vigilant for hepatitis A cases and to provide appropriate vaccination recommendations to high-risk groups.
Prevention Measures
In addition to vaccination, the CHP advises the public to practice good personal and hand hygiene to minimize the risk of infection. This includes thorough handwashing with soap and water after using the toilet and before preparing or eating food.