Certain serious and life-threatening diseases that occur in HIV-positive people are called "AIDS-defining" illnesses. When a person gets one of these illnesses, he or she is diagnosed with the advanced stage of HIV infection known as AIDS.

The Centers for Disease Control and Prevention (CDC) has developed a list of these illnesses (see below). No single patient is likely to have all of these problems. Some of the conditions, in fact, are rare.

• Candidiasis of the esophagus, bronchi, trachea, or lungs [(but NOT the mouth (thrush)]
• Cervical cancer, invasive
• Coccidioidomycosis, disseminated or extrapulmonary
• Cryptococcosis, extrapulmonary
• Cryptosporidiosis, chronic intestinal (greater than one month's duration)
• Cytomegalovirus disease or CMV (other than liver, spleen, or nodes)
• Cytomegalovirus retinitis (with loss of vision)
• Encephalopathy, HIV related
• Herpes simplex: chronic ulcer(s) (more than 1 month in duration); or bronchitis, pneumonitis, or esophagitis
• Histoplasmosis, disseminated or extrapulmonary
• Isosporiasis, chronic intestinal (more than 1 month in duration)
• Kaposi sarcoma
• Lymphoma, Burkitt's (or equivalent term)
• Lymphoma, immunoblastic (or equivalent term)
• Lymphoma, primary, of brain
• Mycobacterium avium complex or M kansasii, disseminated or extrapulmonary
• Mycobacterium tuberculosis, any site (pulmonary or extrapulmonary)
• Mycobacterium, other species or unidentified species, disseminated or extrapulmonary
• Pneumocystis pneumonia (PCP)
• Pneumonia, recurrent
• Progressive multifocal leukoencephalopathy
• Salmonella septicemia, recurrent
• Toxoplasmosis of brain
• Wasting syndrome due to HIV

(Source: Revised classification system for HIV infection and expanded surveillance case definition for AIDS among adolescents and adults. Morbidity and Mortality Weekly Report, December 18, 1992/41 (RR-17), 1993).