A case of post-outbreak acute hepatitis a in a Japanese man who have sex with men infected with RIVM-HAV16-090 strain.

AIM: Hepatitis A outbreaks among men who have sex with men (MSM) are a growing global concern. We present a case report of acute hepatitis A in a Japanese MSM who acquired the infection after the conclusion of a recent hepatitis A outbreak in Japan during his subsequent visit to Taiwan.

CASE PRESENTATION: A 27-year-old male had experienced fever, headache, and loss of appetite over the previous eight days. After his jaundiced skin was noted during a routine health examination, he visited our outpatient department that same day. The severe liver dysfunction detected in blood tests necessitated hospitalization for acute hepatitis. Subsequent tests revealed positive HA-IgM antibodies, confirming acute hepatitis A. Further inquiry revealed the patient's MSM status and recent sexual encounter one and a half months earlier during a visit to Taiwan. With conservative treatment, his condition improved and he was discharged after 12 days. Phylogenetic analysis extracted from his stool sample confirmed that the hepatitis A virus (HAV) strain was RIVM-HAV16-090, consistent with strains observed in previous hepatitis outbreaks among MSM populations.

CONCLUSION

To the best of our knowledge, this is the first case report of acute hepatitis A in a Japanese MSM sporadically infected with the RIVM-HAV16-090 strain since the end of the outbreak. This case underscores the persistent risk of hepatitis A transmission among MSM despite the cessation of the outbreak, emphasizing the importance of targeted vaccination campaigns, sexual health education, and ongoing vigilance in mitigating the risk of hepatitis A transmission among MSM.