Estimating HIV-1 incidence in Japan from the proportion of recent infections

The first step of the UNAIDS/WHO 90-90-90 targets to encourage early diagnosis with treatment for the control of HIV-1 epidemic is to achieve 90% HIV-1 diagnosis in infected individuals. In Japan, approximately 30% of newly reported cases have been annually identified by AIDS onset, implying that substantial numbers of HIV-1-infected individuals remain undiagnosed. However, the proportion of undiagnosed cases has not yet been determined. In the present study, the proportion of recent HIV-1 infections to newly-diagnosed cases was determined from 2006 to 2015 using a recent infection assay for three metropolitan areas in Japan: Tokyo, Osaka, and Fukuoka. Estimated median periods between infection and diagnosis were 1.0, 1.8, and 2.9 years for Tokyo, Osaka, and Fukuoka, respectively. Estimation of annual HIV-1 incidence by a back-calculation method using these data as well as HIV/AIDS national surveillance data indicated proportions of undiagnosed to new HIV-1 infections from 2006 to 2015 to be 18% in Tokyo, 22% in Osaka, 38% in Fukuoka, and 28% in Japan. This is the first report estimating HIV-1 incidence in Japan using a serological biomarker in combination with national HIV/AIDS surveillance data.