What is AIDS?

AIDS, or acquired immunodeficiency syndrome, is a disease that attacks the immune system, your body's main defense against disease. AIDS is caused by a virus known as HIV (or human immunodeficiency virus). First reported in 1981, HIV infection is now a worldwide epidemic, affecting 34 million. According to the Centers for Disease Control and Prevention, 800,000 to 900,000 people in the United States are infected with HIV, and another 40,000 contract the virus every year.

HIV travels from person to person through body fluids such as blood, semen, vaginal fluids, and breast milk. It is most often spread through sex or by sharing needles used to inject drugs into the veins. An infected woman can also pass HIV to her child during birth or breast-feeding. Blood transfusions given to patients before 1986 also spread HIV, but the risk now of getting the virus this way is low-only 1 in 500,000. A person can't catch HIV through casual contact such as hugs, kisses, or handshakes.

When HIV first invades the body, it causes minor damage to cells in your immune system. You may not have symptoms, or you may have only a few symptoms at first; these symptoms often go away for months or even years. During all that time, though, HIV continues its assault. As the immune system weakens, it can no longer fully protect the body from germs and other invaders. When the damage reaches a certain point, the HIV infection turns into AIDS, and life-threatening diseases such as pneumonia or cancer may soon follow.

There's no cure for AIDS, but you can do a lot to prevent the disease in the first place. And if you have tested positive for HIV, or even if you have full-blown AIDS, you can do a lot to slow the progress of the disease and stay healthy longer. New research and treatments also hold great promise: They may soon make AIDS a chronic-not a fatal-disease.

Symptoms:

The first symptoms of HIV infection are similar to those of mononucleosis-fatigue and swollen glands, which set in within a month or two after you're first infected. These symptoms often go away in one to two weeks. One to 10, or sometimes more, years may pass before more serious symptoms appear, depending on many factors-chiefly how healthy your immune system is. When symptoms do occur, they progress slowly.

When HIV first occurs:

• Sore throat, fever, skin rash, or swollen lymph nodes (most often in the neck, under the arms, or in the groin) that may last for several weeks.

• Fatigue, overall sick feeling as with the flu.

As HIV turns into AIDS (T-cell count falls to 200):

• Chronic fever (over 100 degrees), chills, and night sweats.

• Frequent colds.

• Cold sores and fungal and yeast infections (also called candida) in the mouth.

• Sudden weight loss-more than 10 percent of body weight in six to eight weeks.

• Chronic diarrhea.

• Dry cough.

• Sores anywhere on the skin or mouth, mostly the round brown, reddish, or purple sores of Kaposi's sarcoma, a form of cancer.

• Last symptoms: rapid vision loss, confusion, memory loss, and personality changes caused by dementia, a sign that HIV has invaded the brain.

If you think you have HIV, get tested. Your doctor or local health department can tell you where to go. Blood tests will show if you've developed antibodies, cells that fight HIV. Someone with HIV antibodies in the blood or urine is said to be HIV-positive. These tests also count your T helper cells; the lower the number, the more damaged your immune system is. Healthy people have a T-cell count of about 1,000.

You can test yourself at home with anonymous blood tests that you can buy over the phone or at some drugstores. To do the test, you prick your finger and make a blot of blood on a test card. You then mail the card to the company. After a few days, usually a week, you can call a toll-free number for your results. You are identified by number only, so the test results remain secret.