Scary because: the virus that causes AIDS (the human immunodeficiency virus, or HIV) is transmitted through blood or body fluids, and it attacks your immune system itself. AIDS is also scary because it takes time for any symptoms to appear, so people can transmit it without knowing it. The disease is very widespread, and there is as yet no vaccine or cure.

Symptoms: Soon after exposure, some people get flu-like symptoms - fever, headache, sore muscles, stomach ache, sometimes with swollen lymph glands or a skin rash. Other people have no symptoms. People with HIV can stay healthy for ten years or longer, but eventually AIDS will manifest in fevers, night sweats, diarrhea, or swollen lymph nodes. HIV damages the immune system so that any opportunistic infection can prove fatal.

What is happening: Most people get the HIV virus by having sex with an infected person, or sharing a hypodermic needle with someone who's infected. Infected mothers can also pass the virus to their unborn children, or to born children via breast milk.


After exposure, the virus multiplies in your body for weeks or months before your immune system responds. During this time, you won't test positive for HIV, but you can infect other people.

When your immune system responds, it starts to make antibodies. Once you
start making antibodies, you will test positive for HIV.

Over time HIV slowly damages your immune system. This damage is typcially measured by the number of
CD4+ ("T-helper") cells you have in a milliliter of blood. Healthy people have cell counts somewhere between 500 and 1,500. In people with HIV, the number slowly declines, and when the count gets below 250 or so, serious health problems may ensue.