Isn't it only a problem for adults?

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).

The only known way for HIV to be transmitted from one person to another is when it is spread from the inside of an infected person's body to the inside of another person's body. This can happen when infected fluids — such as semen (also known as "cum," the fluid released from the penis when a male ejaculates), vaginal fluids, or blood — are passed from one person to another. Someone can become infected even if only tiny amounts of these fluids are spread.

How does someone become infected? HIV can be spread through sexual intercourse if one of the partners has the virus. It can be spread through an infected person's blood, semen, and secretions from the cervix (part of a female's uterus) or vagina.

HIV can travel to another person through cuts and sores on the penis, rectum (the last part of the intestine that connects to the anus), vagina, or skin around the genitals and probably the mouth and other mucous membranes. These cuts or sores are often so small that a person isn't even aware of them.

Girls and guys who have a discharge (an abnormal fluid coming from the vagina or penis) or genital sores because they have a sexually transmitted disease (STD) are at increased risk for infection. HIV can be spread sexually from a man to a woman, a woman to a man, a man to a man, and a woman to a woman.

People who inject themselves with drugs also risk infecting themselves with HIV. Many people who use needles to take intravenous drugs or steroids share the needles with others. A person 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.