Which virus is the cause of AIDS?

Which virus is the cause of AIDS? Human immunodeficiency virus, or HIV, causes AIDS when untreated infection progressively damages the immune system.

HIV is an enveloped retrovirus in the genus Lentivirus. It primarily targets CD4-positive T cells, along with macrophages and dendritic cells. By infecting and destroying or impairing these immune cells, HIV gradually reduces the body’s ability to control infections and certain cancers. AIDS is the advanced clinical stage of HIV infection, not a separate virus.

There are two recognized human types: HIV-1 and HIV-2. HIV-1 is more transmissible and causes the vast majority of infections worldwide, while HIV-2 is concentrated mainly in West Africa. Both viruses are believed to have originated from simian immunodeficiency viruses in African primates after separate cross-species transmissions.

AIDS was first recognized as a clinical syndrome in 1981, and researchers identified HIV as its cause in the early 1980s. Modern antiretroviral therapy can suppress HIV to undetectable levels, prevent progression to AIDS, and dramatically reduce transmission risk. HIV is not spread by casual contact such as hugging, sharing utensils, or ordinary social interaction.