How is HIV Transmitted?

HIV enters the body through open cuts, sores, or breaks in the skin; through mucous membranes, such as those inside the anus or vagina; or through direct injection. There are several ways by which this can happen:
Sexual contact with an infected person. This is the primary focus of this lesson and is reviewed in greater detail in the following sections.
Sharing needles, syringes, or other injection equipment with someone who is infected.

Mother-to-child transmission. Babies born to HIV-positive women can be infected with the virus before or during birth, or through breastfeeding after birth. More information about HIV and pregnancy can be found in this lesson.

Transmission in health care settings. Healthcare professionals have been infected with HIV in the workplace, usually after being stuck with needles or sharp objects containing HIV-infected blood. As for HIV-positive healthcare providers infecting their patients, there have only been six documented cases, all involving the same HIV-positive dentist in the 1980s.

Transmission via donated blood or blood clotting factors. However, this is now very rare in countries where blood is screened for HIV antibodies, including in the United States.

Since the beginning of the HIV/AIDS epidemic, new or potentially unknown routes of transmission have been thoroughly investigated by state and local health departments, in collaboration with the U.S. Centers for Disease Control and Prevention (CDC). To date, no additional routes of transmission have been recorded, despite a national system designed to detect unusual cases.