Hong Kong Confirms Hepatitis A Cluster

The Centre for Health Protection (CHP) of the Department of Health announced today that it is investigating a cluster of 24 hepatitis A infections linked by identical viral genetic sequences, detected in Hong Kong between September 2025 and February 2026.

These cases primarily affect men, a significant portion of whom identify as men who have sex with men (MSM). Epidemiological investigations found no common residences or restaurants among the patients, leading authorities to note that male-to-male sexual contact cannot be ruled out as a transmission factor.

Dr. Edwin Tsui, Controller of the CHP, emphasized in a media release on March 11, 2026, that hepatitis A outbreaks among MSM populations have occurred globally in the past, including a similar transmission chain in Hong Kong from 2015 to 2017, which was controlled through targeted vaccination.

To curb the spread of this infection, the CHP urges high-risk groups, particularly MSM, to receive vaccinations with two doses of the hepatitis A vaccine. In response to the current cluster, the CHP will begin offering two free doses of the vaccine to eligible MSM residents of Hong Kong starting March 12, 2026.

Epidemic hepatitis A is primarily spread through the ingestion of contaminated food or water, or via contaminated hands before eating. However, it can also be transmitted through high-risk sexual contact. Symptoms, such as fever, fatigue, abdominal pain, nausea, diarrhea, and jaundice, typically appear 14 to 50 days after infection due to the virus's long incubation period.

For international travelers departing from the United States for Hong Kong, the CDC recommends that unvaccinated travelers also receive the Hepatitis A vaccine. And travelers allergic to a vaccine component should receive a single dose of immune globulin, which provides effective protection for up to 2 months, depending on the dosage given.

Additionally, unvaccinated travelers who are over 40 years old, are immunocompromised, or have chronic medical conditions, and who are planning to depart for a risk area in less than 2 weeks, should receive the initial dose of vaccine and, at the same appointment, receive immune globulin.

Recently, Hong Kong has reported increased risks of chikungunya.

The CDC also recommends various routine and travel vaccinations before visiting Hong Kong in 2026.