HIV-2 was first identified in 1986 in West Africa. Although the modes of transmission are similar to HIV-1 and are associated with the same opportunistic infections and AIDS, immunodeficiency develops more slowly and is milder.

Furthermore, those with HIV-2 are less infectious in the early course of infection, and HIV-2 infection in children is rare as it seems to be less transmissible from mother to child.

In September, the Ministry of Health, Labor and Welfare announced that the first case of a Japanese national testing positive for HIV-2 had been confirmed. He had received a blood transfusion West Africa where HIV-2 is most prevalent.

Previous cases of HIV-2 in Japan were among non-Japanese.