What Is AIDS ? AIDS is the late stage of HIV infection that occurs when the body’s immune system is badly damaged because of the virus. In the U.S., most people with HIV do not develop AIDS because taking HIV medicine as prescribed stops the progression of the disease. A person with HIV is considered to have progressed to AIDS when: Discover how HIV spreads, how to prevent the virus progressing to AIDS , and where to get treatment. AIDS , transmissible disease of the immune system caused by the human immunodeficiency virus (HIV). HIV is a lentivirus (literally meaning “slow virus”; a member of the retrovirus family) that slowly attacks and destroys the immune system, the body’s defense against infection, leaving an individual vulnerable to a variety of other infections and certain malignancies that eventually cause death. AIDS is the final stage of HIV infection, during which time fatal infections and cancers ... Overview Acquired immunodeficiency syndrome ( AIDS ), is an ongoing, also called chronic, condition. It's caused by the human immunodeficiency virus, also called HIV. HIV damages the immune system so that the body is less able to fight infection and disease. If HIV isn't treated, it can take years before it weakens the immune system enough to become AIDS . Thanks to treatment, most people in the U.S. don't get AIDS .