AIDS stands for Acquired Immune Deficiency Syndrome. AIDS is the most advanced stage of HIV infection. The US Centers for Disease Control and Prevention (CDC) defines a person as having AIDS if she or he is living with HIV (HIV+) and has a CD4 cell  count of 200 or less. The CDC has also developed a list of opportunistic infections (OIs) , cancers , and conditions that are considered AIDS-defining conditions (see below). If you have HIV and one or more of these infections or conditions, you have a diagnosis of AIDS, no matter what your CD4 count is or how it changes in the future.
Click above to view or download this fact sheet as a PDF slide presentation 
AIDS is also sometimes referred to as 'stage 3 HIV.' The CDC defines and uses 'stages' of HIV mainly to keep track of the amount of HIV infection in the US and to plan for prevention and care on a population level. These definitions are not meant for health providers to use in making clinical decisions for individual patients.
The World Health Organization (WHO) uses a similar staging system and set of definitions. The WHO refers to AIDS as severe HIV and calls severe HIV or AIDS 'stage 4.' Nevertheless, it defines AIDS as occurring in people living with HIV who have CD4 counts of 200 or less or one of the AIDS-defining conditions listed below (same as CDC definition).
This list of AIDS-defining conditions comes from a government report and contains medical terms. If you have any questions, ask your health care provider or contact an educator at a local AIDS service organization (ASO). In the US, you can find an ASO by using POZ's Health Services Directory . To find services across the world, visit AIDSmap's e-atlas .
- Bacterial infections, multiple or recurrent (only for children less than 13 years old)
- Candidiasis (type of yeast infection ) of bronchi, trachea, or lungs
- Candidiasis, esophageal
- Cervical cancer , invasive (only among people 13 years old or older)
- Coccidioidomycosis, disseminated or extrapulmonary
- Cryptococcosis, extrapulmonary
- Cryptosporidiosis, chronic intestinal (for longer than 1 month)
- Cytomegalovirus disease (other than liver, spleen, or nodes), beginning when older than one month
- Cytomegalovirus retinitis (with loss of vision)
- Encephalopathy, HIV-related
- Herpes simplex: chronic ulcers (lasting longer than 1 month); or bronchitis, pneumonitis, or esophagitis (beginning when older than one month)
- Histoplasmosis, disseminated or extrapulmonary
- Isosporiasis, chronic intestinal (for longer than 1 month)
- Kaposi sarcoma
- Lymphoma, Burkitt (or equivalent term)
- Lymphoma, immunoblastic (or equivalent term)
- Lymphoma, primary, of brain
- Mycobacterium avium complex or M. kansasii, disseminated or extrapulmonary
- Mycobacterium tuberculosis , of any site, pulmonary (only among people 13 years old or older), disseminated, or extrapulmonary
- Mycobacterium, other species or unidentified species, disseminated or extrapulmonary
- Pneumocystis jirovecii pneumonia (PCP)
- Pneumonia , recurrent (only among people 13 years old or older)
- Progressive multifocal leukoencephalopathy
- Salmonella septicemia, recurrent
- Toxoplasmosis of brain, beginning when older than one month
- Wasting syndrome due to HIV