The identification of HIV

AIDS is caused by a virus that was identified in France in 1983 and in the United States in 1984. This was called either lymphadenopathy-associated virus (LAV) or human T-cell lymphotropic virus type III (HTLV-III). Since 1986, it has generally been referred to as HIV.

In 1984, a test for detecting antibodies to HIV was developed. Early use of the test indicated that only a small proportion of people with HIV had gone on to develop AIDS. AIDS is at one end of a spectrum that can range from clinical wellbeing and asymptomatic infection to life-threatening opportunistic illness.

In 1986, HIV-2 was discovered. Though it has a different geographical distribution and pathogenicity than HIV-1, the same advice about transmission, prevention, safer sex, and hygiene apply equally. HIV-2 is associated with a slower and more benign disease course and is somewhat harder to transmit than HIV-1. It is seen predominantly in West Africa.

HIV produces billions of viral particles every day. With replication, viral mutations (mistakes) occur, so that there is a great diversity of HIV. Diversity also comes through the combination of different viral strains. HIV strains are divided into three groups, based on genetic similarity. The largest of these is group M (main). The other two are group O (outlier) and group N (non-M and non-O).

Within group M are many subtypes, known as clades. Subtype B is predominant in the Americas, Europe, Australia and Japan. Subtype C is found in South Africa, India and China. Subtype E is predominant in Thailand. Differences in clade do not affect response to antiretroviral treatment, but do complicate the challenge of developing an effective vaccine against HIV.