A disease of the immune system due to infection with HIV. HIV destroys the CD4 T lymphocytes (CD4 cells) of the immune system, leaving the body vulnerable to life-threatening infections and cancers. Acquired immunodeficiency syndrome (AIDS) is the most advanced stage of HIV infection. To be diagnosed with AIDS, a person with HIV must have an AIDS-defining condition or have a CD4 count less than 200 cells/mm3 (regardless of whether the person has an AIDS-defining condition).
In people with AIDS, ART improves the immune system and substantially increases life expectancy. Many patients treated with ART have near-normal life expectancies. ART is a treatment that patients must continue for life. It is not a cure. It is possible for HIV to become resistant to some antiretroviral medications. The best way to prevent resistance is for the patient to take their ART as directed without fail. If the patient wants to stop a drug because of side effects, he or she should call the physician immediately.