Why does aids not manifest itself for up to 10 years?

The following answer is from AmFar and appears in The Body's Section entitled Understanding HIV/AIDS:

Acquired Immunodeficiency Syndrome (AIDS) is a condition that gradually destroys the body's immune defense system and makes the body vulnerable to opportunistic diseases. It is caused by infection with the Human Immunodeficiency Virus (HIV). After HIV invades the body, it lives and multiplies in the white blood cells, which are the cells that protect the body from disease. As the virus multiplies, it damages or kills these and other cells, and the body becomes prey to a wide range of disease-causing microbes. When HIV has destroyed enough white blood cells, the body is no longer able to fight off many infections, and a person begins to get sick. If a person with HIV infection has not had many white cells die, that person feels fine and looks fine. That person is asymptomatic (that is, has no symptoms of AIDS), but can still give the virus to someone else. People who are infected with HIV can be asymptomatic, looking and feeling well for ten years or even longer. That is why the practice of safer sex is vitally important, even with people who seem to be well. As more and more white cells die, the HIV-infected person begins to get sick and is then said to be symptomatic. When there are very few white cells left, particularly of the kind called CD4+, and one or more serious diseases start occurring, the HIV-infected person has AIDS.

Hope this helps!

DR