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. Anal or vaginal intercourse without a condom with a partner who is either positive or does not know his or her HIV status account for the vast majority of sexually-transmitted HIV cases in the U.S. and elsewhere. Oral sex is not an efficient route of HIV transmission. To learn more about the "theoretical risk" of oral sex and HIV transmission, click here. Kissing, massage, masturbation and "hand jobs" do not spread HIV. More information about safer sex to help prevent HIV transmission can be found here.
- Sharing needles, syringes or other injection equipment with someone who is infected. Information on safer injecting to help prevent the spread of HIV can be found here.
- 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 here.
- 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.
HIV has been detected in saliva, tears and urine. However, HIV in these fluids is only found in extremely low concentrations. What's more, there hasn't been a single case of HIV transmission through these fluids reported. HIV cannot be transmitted through day-to-day activities such as shaking hands, hugging or casual kissing. You cannot become infected from a toilet seat, drinking fountain, or sharing food or eating utensils with someone who is positive. You also cannot get HIV from mosquitoes.
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.