As of 2009, 8,100 people were estimated to be living with HIV and AIDS in Japan, of whom 2,700 or one-third comprised women [1]. The number of people living with HIV since 1996 has steadily grown with 1,075 new cases of HIV and 469 new cases of AIDS reported in 2010 [2]. The new cases of HIV involved 997 Japanese nationals and 78 foreign nationals [2].  The cities with the highest rates of infection per 100,000 population in 2010 were Tokyo (3%) and Osaka (2.2%) [2]. Japan's HIV and AIDS caseload has remained low by global standards, with the estimated prevalence at less than 0.1% [1].

The key affected population most considered to be at risk of HIV in Japan are men who have sex with men (MSM). More than two-thirds (69.2%) of the reported HIV cases in 2010 were attributed to homosexual transmission, while heterosexual transmission accounted for less than a fifth (18.1%) [3]. The number of HIV cases among men due to homosexual contact rose dramatically between 2000 and 2007, particularly among those aged 20-29 years and even more so among those aged 30-39 years [4]. The number of new AIDS cases that resulted from homosexual contact also increased substantially during same period.  A recent study of 2,573 men, mostly Japanese in their late-30s and infected through male-to-male sexual contacts, found an increasing trend in prevalence from 5.9% (16/273) in 2003 to 8.3% (50/605) in 2008 [5].

Further in 2008, the most recent year for which age disaggregated data are available, 70% of cases reported were among those aged 20-39 years, with most cases found in males aged 25-34 years and females aged 20-24 years, for both Japanese and foreign nationals [3].  Injecting drug use and mother-to-child transmission together accounted for less than 1% of cases [3]. However, the situation regarding injecting drug users (IDUs) and sex workers has yet to be fully assessed. In addition, although to a lesser extent, migrant workers – especially unregistered non-Japanese nationals without legal status – are considered vulnerable and at risk of HIV infection [6].

Young people are vulnerable to HIV. A 2006 study of attitudes toward sex and sexual behaviour by 978 students who were visiting the health services centre of a college for medical check-ups found that 90% of males and 83% of females had anticipated having a sexual intercourse before marriage, while 8% of male students and 3% of female students indicated that it was not wrong to have extramarital sexual intercourse after marriage [7].  Seventy-five per cent of sexually experienced students reported that they used a condom during their first sexual intercourse, while 73% reported using a condom during their most recent sexual intercourse [7]. The more sexual partners the students had up to the time of the study, the less condom use they reported for both their first and most recent sexual encounters[7].

Sources:

[1] UNAIDS, Report on the Global AIDS Epidemic, 2010

[2] Japan, Committee on AIDS Trends, Ministry of Health, Labour and Welfare, 2010

[3] Japan, UNGASS Country Progress Report, 2010

[4] National AIDS Surveillance Committee, Ministry of Health, Labour and Welfare, Annual Report on HIV/AIDS Surveillance in Japan, 2010

[5] Hattori J, Shiino T, Gatanaga H, et al. Trends in transmitted drug-resistant HIV-1 and demographic characteristics of newly diagnosed patients: Nationwide surveillance from 2003 to 2008 in Japan. Antiviral Research, Volume 88, Issue 1, October 2010, Pages 72-79 

[6] Japan Center for International Exchange, Japan’s Response to the Spread of HIV and AIDS, 2004

[7] Yamamoto K, 2006. Cross-sectional study on attitudes toward sex and sexual behavior among Japanese college students. Journal of Physiological Anthropology;25(3):221-7