CDC case definitions

In 2008, surveillance case definitions from the US Centers for Disease Control and Prevention (CDC) were revised to require laboratory-confirmed evidence of HIV infection for all those aged 18 months and older. It is stressed throughout the document that case definitions are for surveillance purposes only and not as a guide for clinical diagnosis.1

The former matrix system used for adults and adolescents (three CD4 cell count ranges and three clinical categories, resulting in nine mutually exclusive categories), has been replaced by a combined case definition for HIV infection and AIDS. The 24 AIDS-defining conditions have not changed.

For those with laboratory confirmation of HIV without an AIDS-defining condition, staging is done according to CD4 cell count. Those who have laboratory confirmation of HIV with an AIDS-defining condition are considered to have stage 3 (AIDS) infection. Stage unknown includes all individuals for whom there is laboratory confirmation of HIV, but no further information about CD4 cell counts, CD4 cell percentages, or the presence of any AIDS-defining condition.

If CD4 cell count and percentage fall into two different infection stages, the more severe stage is assigned. Further information on the diagnosis of AIDS-defining conditions can be found in appendix C of the 1993 revised HIV classification system, available at the CDC website

Adults and teens

The following criteria apply to all individuals aged 13 years and older. For the purpose of surveillance, reportable cases of HIV infection fall into one of four stages, each requiring laboratory confirmation of HIV infection. The presence of an AIDS-defining condition alone is insufficient to meet the case definition for HIV for reporting purposes. Staging is not bi-directional. If someone's CD4 count or percentage rises or an AIDS-defining condition is successfully treated, for surveillance purposes there is no reclassification into a less severe stage.

Stage 1: No AIDS-defining condition and either a CD4 cell count at or above 500 cells/mm3 or CD4 cell percentage at or above 29%.

Stage 2: No AIDS-defining condition and either a CD4 cell count of 200 to 400 cells/mm3 or CD4 cell percentage in the range 14 to 28%.

Stage 3 (AIDS): A documented AIDS-defining condition or a CD4 cell count less than 200 cells/mm3 or a CD4 cell percentage under 14%. 

Stage Unknown: Laboratory confirmation of HIV infection, but no information on CD4 cell count, CD4 cell percentage, or the presence of an AIDS-defining condition.


The Centers for Disease Control and Prevention (CDC) surveillance case definition for HIV in children under the age of 18 months was amended in 2008. Laboratory and other criteria now exist for a finding of indeterminate, presumptive, and definitive HIV infection. Nucleic acid amplification tests (either RNA-PCR or DNA-PCR) are the preferred method to either exclude or diagnose HIV infection in this age group.1

The CDC case definition for surveillance in those aged 18 months up to 13 years requires either:

  • A positive result from an HIV antibody screening test, confirmed by a positive result from a supplemental HIV antibody test (e.g. Western blot or indirect immunofluorescence assay) or
  • A positive virological test for HIV or its components using PCR-RNA, PCR-DNA, HIV p24 antigen test, or HIV viral culture.

Children aged 18 months to less than 13 years whose exposure to HIV was not perinatal, should be tested using an HIV antibody test in lieu of virologic testing, as a negative or nonreactive virological result does not rule out possible infection. 

Children aged 18 months to less than 13 years of age must have laboratory-confirmed evidence of HIV infection to meet the surveillance case definition for HIV infection and AIDS. Diagnostic criteria alone are no longer accepted for surveillance purposes. 

There were no changes made in the revised 1994 list of AIDS-defining conditions for children under the age of 13.3 The clinical staging system can be found in the section HIV treatment in children.  

CDC AIDS-defining conditions

  • Candidiasis of bronchi, trachea, or lungs
  • Candidiasis of oesophagus, may be diagnosed presumptively
  • Cervical cancer, invasive, in those aged 13 or older
  • Coccidioidomycosis, disseminated or extrapulmonary
  • Cryptococcosis, extrapulmonary
  • Cryptosporidiosis, chronic intestinal for more than 1 month
  • Cytomegalovirus disease, other than liver, spleen, or nodes, onset after one month of life
  • Cytomegalovirus retinitis (with loss of vision), may be diagnosed presumptively
  • Encephalopathy, HIV related
  • Herpes simplex: chronic ulcers for more than 1 month or bronchitis, pneumonitis, or oesophagitis with onset after 1 month of life
  • Histoplasmosis, disseminated or extrapulmonary
  • Isosporiasis, chronic intestinal for more than 1 month
  • Kaposi's sarcoma, may be diagnosed presumptively
  • Lymphoma, Burkitt (or equivalent term)
  • Lymphoma, immunoblastic (or equivalent term)
  • Lymphoma, primary, of brain
  • Mycobacterium avium complex or Mycobacterium kansasii, disseminated or extrapulmonary, may be diagnosed presumptively
  • Mycobacterium tuberculosis of any site (pulmonary, disseminated, or extrapulmonary) in those aged 13 years or older, may be diagnosed presumptively
  • Mycobacterium, other species or unidentified species, disseminated or extrapulmonary, may be diagnosed presumptively
  • Pneumocystis jirovecii pneumonia, may be diagnosed presumptively
  • Pneumonia, recurrent, only in those aged 13 years or older; may be diagnosed presumptively
  • Progressive multifocal leukoencephalopathy
  • Salmonella septicemia, recurrent
  • Toxoplasmosis of brain, onset after 1 month of life, may be diagnosed presumptively
  • Wasting syndrome attributed to HIV

AIDS-defining condition only in persons under 13 years of age:

  • Bacterial infections, multiple or recurrent
  • Lymphoid interstitial pneumonia or pulmonary lymphoid hyperplasia complex, may be diagnosed presumptively

Acute infection

Acute HIV infection occurs during the time from viral acquisition until seroconversion (presence of measurable levels of HIV-specific antibodies). During acute infections, 40 to 80% of people will develop symptoms of a non-specific viral illness (e.g., fever, fatigue, or rash) that usually last one to two weeks.

Documented evidence of detectable HIV RNA or DNA or of p24 antigen in plasma or serum in the presence of a documented negative or indeterminate result from an HIV antibody test is required for a diagnosis of acute HIV infection. The laboratory tests should be conducted on the same specimen or on specimens obtained on the same day.1


  1. Centers for Disease Control and Prevention (CDC) Male Latex Condoms and Sexually Transmitted Diseases. CDC, Atlanta, GA, 2002
  2. Centers for Disease Control and Prevention (CDC) 1993 revised classification system for HIV infection and expanded surveillance case definition for AIDS among adolescents and adults. MMWR Recomm Rep 41(RR-17):1-19, 1992
  3. Centers for Disease Control and Prevention (CDC) 1994 revised classification system for human immunodeficiency virus infection in children less than 13 years of age. MMWR Recomm Rep 43(RR-12): 1-10, 1994
Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.