To become infected with HIV , infected blood, semen or vaginal secretions must enter your body. This can happen in several ways: By having sex. You may become infected if you have vaginal, anal or oral sex with an infected partner whose blood, semen or vaginal secretions enter your body.

Where did AIDS come from and how did it start?

HIV infection in humans came from a type of chimpanzee in Central Africa. The chimpanzee version of the virus (called simian immunodeficiency virus, or SIV) was probably passed to humans when humans hunted these chimpanzees for meat and came in contact with their infected blood.

What is the main cause of AIDS?

HIV infection is caused by the human immunodeficiency virus. You can get HIV from contact with infected blood, semen, or vaginal fluids. Most people get the virus by having unprotected sex with someone who has HIV. Another common way of getting it is by sharing drug needles with someone who is infected with HIV.