Outbreak of hepatitis A linked to European outbreaks among men who have sex with men in Osaka, Japan, from March to July 2018

Aim Ongoing hepatitis A outbreaks among men who have sex with men (MSM) have been reported worldwide, mainly in Europe, since 2016. In Japan, there has been an increase in the number of notified hepatitis A cases since January 2018, most of which were suspected to have been transmitted through homosexual contact. In this paper, we describe the current outbreak situation of hepatitis A among MSM. Methods Between March and July 2018, 13 cases of hepatitis A were identified in our hospital. All cases were identified as MSM. Data on clinical and laboratory findings and therapies were collected from medical records. Serum or stool samples were obtained from 13 patients and subjected to sequence analysis. Results Of all patients, 12 reported to have male-to-male homosexual contact within 7 weeks prior to symptom onset, and 6 visited sex-on-premises venues in the same area. Furthermore, 12 patients were infected with HIV and consequently received antiretroviral therapy with sustained viral suppression. Ten patients received pulsed methylprednisolone therapy. Plasma exchange was additionally carried out in one patient. All patients received inpatient hospital care and were discharged alive. Sequence information, which was available in all cases, showed that the hepatitis A virus strain was identical to the EuroPride strain (RIVM-HAV16-090). Conclusions Results of sequence analysis suggest that the ongoing hepatitis A outbreak among MSM in Japan is linked to the 2016 European outbreaks. A vaccination program is urgently required for high-risk populations to control this ongoing outbreak.