HIV is a virus that lives in human blood, sexual fluids, and breast milk. It weakens your immune system, so your body has a hard time fighting off common germs, viruses, fungi, and other invaders. It spreads mainly through unprotected sexual contact and sharing needles.
AIDS -- acquired immune deficiency syndrome -- is the condition that comes when your immune system stops working and you get sick because of HIV.
Who Gets It?
The infection spreads from person to person when certain body fluids are shared, usually during vaginal or anal sex, or when sharing drugs you inject. It can also be passed from dirty needles from tattoos and body piercing. It can be spread through oral sex, too, although the chance is small.
A mother can pass HIV to her child during birth, when the baby is exposed to her infected blood, or in her breast milk. But in some areas of the developing world, it's safer for a mom with HIV to breastfeed than to give a newborn contaminated water.
HIV doesn't live in saliva, tears, pee, or sweat -- so it can't be spread by casual contact with these body fluids.
It's actually not as easy to get as other infectious diseases. The virus can't survive for long outside the human body; it dies quickly when the body fluid dries up. It's not spread by animals or insects. You won't find it on public surfaces like door handles or toilet seats.
All blood products used in the United States and Western Europe today are tested for HIV. Blood banks get rid of any donated blood that tests positive, so it never gets into the public supply. Someone who donates HIV-positive blood will be contacted so they can be tested by their doctor, and they won't be able to give blood again.
Where Is It Widespread?
Sub-Saharan Africa (the southern part) has the greatest number of people who are infected. The World Health Organization and the United Nations' UNAIDS office estimate that more than a third of adults are infected with HIV in some areas of Africa. The number of people in Eastern Europe and Asia who have HIV is growing quickly.
There are two main types of the virus: HIV-1 and HIV-2. HIV-2 is most commonly found in West Africa, although places in other parts the world are seeing it, too. HIV tests usually look for both kinds.
