HIV lives in an infected person's blood , tissues, organs, and certain body fluids (semen or vaginal fluid and anal mucus).1,2 Nursing mothers who are infected also have HIV in their breast milk. HIV spreads between people through blood and body fluids.
There are several common ways that HIV can be passed from person to person, including:
- Having unprotected sex with someone who is infected. Worldwide, most new HIV infections occur through sex.3 Women are particularly at risk of infection through sex. It's much easier to get HIV (or to give it to someone else) if a person has a sexually transmitted disease (STD). For more information, see the Centers for Disease Control and Prevention's The Role of STD Detection and Treatment in HIV Prevention.
- Transmission from mother to child. Without anti-HIV treatment, an infected mother may pass the virus to her child during pregnancy, birth, or breastfeeding. Although mother-to-child transmission is preventable, and transmission is rare in the United States, more than 300,000 infants are infected each year through their mothers globally; most of these infections occur in sub-Saharan Africa.
- Using needles or syringes that have been used by people who are infected.
- Pre-chewing food for infants. In a few cases, HIV has been spread when HIV-infected caregivers chewed food (or warmed it in their mouths) and then fed the food to an infant. This practice can expose the child to HIV if the caregiver has a sore or cut in the mouth. The CDC recommends that HIV-infected caregivers do not pre-chew food for infants.4
- Receiving infected blood products or transplanted organs. Since 1985, the United States tests all donated blood and organs for HIV; therefore, the risk of getting HIV in this way in the United States is now extremely low, and the risk is also decreasing in other countries as they improve their testing methods. For more information, see the CDC's How safe is the blood supply in the United States?