HIV attacks the body’s immune system, its defense against disease, and weakens it over time. A person who has HIV gradually loses the protection of his or her immune system and the person begins to experience health problems. These may be fairly small problems at first --skin problems or yeast infections-- but over time the illnesses become more serious. The amount of time that it takes HIV to begin to affect a person’s health varies widely from one individual to another. When a person is diagnosed with one of the serious illnesses or cancers which are “AIDS-defining”, the person is then said to have AIDS.

HIV attacks the immune system chiefly by damaging the CD4 (also known as T4 or T-helper) cells which help the body fight off diseases. HIV can also have direct effects upon the body. For example, the virus can attack cells in the brain and impair the brain’s function.

Information provided by AIDS Committee of Toronto website.