AIDS stands for acquired immunodeficiency syndrome, a disease that makes it difficult for the body to fight off infectious diseases. The human immunodeficiency virus (HIV) causes AIDS by infecting and damaging part of the body's defenses against infection, namely the white blood cells known as CD4 helper lymphocytes (pronounced: lim-fuh-sites).

How does someone become infected? HIV can be spread through any type of unprotected sex (oral, vaginal, or anal) if one of the partners has the virus. This can happen when body fluids such as semen (cum), vaginal fluids, or blood from an infected person get into the body of someone who is not infected. Someone can become infected even if only tiny amounts of these fluids are spread. Everyone who has unprotected sex with an infected person is at risk of contracting HIV, but people who already have another sexually transmitted disease (STD) are even more at risk.

HIV can be spread sexually from a guy to a girl, a girl to a guy, a guy to a guy, and a girl to a girl.

Sharing needles to inject drugs or steroids is another way that HIV can be passed to other people. Sharing of needles for tattoos, piercings, and body art can also lead to infection. Someone with HIV who shares a needle also shares the virus, which lives in the tiny amounts of blood attached to the needle. Sharing needles also can pass hepatitis and other serious infections to another person.

Also, newborn babies are at risk of getting the HIV virus from their mothers if they're infected. This can happen before the baby is born, during birth, or through breastfeeding. Pregnant teens and women should be tested for HIV because infected women who receive treatment for HIV are much less likely to spread the virus to their babies. Babies born to mothers infected with HIV are also given special medicines to try to prevent HIV infection.

Protecting Yourself

The best way to protect yourself from HIV is to abstain from oral, vaginal, and anal sex and to not share needles.

If you do have sex, using latex condoms properly every time can help protect you. Condoms work by providing a barrier to the body fluids that can be shared during sexual activity (including oral sex). Always follow the directions exactly and never use the same condom twice. If you have had unprotected sex (sex without a condom) or have shared needles with someone else, you should be tested for HIV. If you've had sex with a condom, you also should be tested since condoms are effective when used correctly, but are not perfect. And ask your partner to be tested as well.

Asking people if they have HIV is not a reliable way of finding out whether they are infected. People may not answer truthfully. They may be embarrassed to tell you or may not want you to know. Or they may not even know they have the virus because it can take many years for symptoms to develop. An infected person will look healthy for many years and can still spread the virus.

Many places, such as doctors' offices, health departments, hospitals, and sites that specialize in HIV testing, can provide more information about HIV and AIDS, personal counseling, and, testing. Talk with your doctor about any questions or concerns you might have.

Reviewed by: Larissa Hirsch, MD
Date reviewed: January 2011