The Centers for Disease Control and Prevention (CDC) classify HIV-infected children either according to their immunological status (using CD4 cell counts and percentages) or their clinical status (based on physical health and symptoms)^[1].

Immunological categories

Very young children normally have much higher CD4 counts than adults. The classification system for HIV-positive based on their CD4 levels therefore takes account of the child's age.

Children aged less than twelve months

Children are assigned to:

• Category 1 (no immunosuppression): CD4 cell count greater than 1499 cells/mm³ or CD4 percentage greater than 25%.

• Category 2 (moderate immunosuppression): CD4 cell count between 740 and 1499 cells/mm³ or CD4 percentage between 15 and 24%.

• Category 3 (severe immunosuppression): CD4 cell count below 750 cells/mm³ or CD4 percentage below 15%.

Children aged one to five years

Children are assigned to:

• Category 1 (no immunosuppression): CD4 cell count greater than 999 cells/mm³ or CD4 percentage greater than 25%.

• Category 2 (moderate immunosuppression): CD4 cell count between 500 and 999 cells/mm³ or CD4 percentage between 15 and 24%.

• Category 3 (severe immunosuppression): CD4 cell count below 500 cells/mm³ or CD4 percentage below 15%.

Children aged six to twelve years

Children are assigned to:

• Category 1 (no immunosuppression): CD4 cell count greater than 500 cells/mm³ or CD4 percentage greater than 25%.

• Category 2 (moderate immunosuppression): CD4 cell count between 200 and 499 cells/mm³ or CD4 percentage between 15 and 24%.

• Category 3 (severe immunosuppression): CD4 cell count below 200 cells/mm³ or CD4 percentage below 15%.

Clinical categories

Children are assigned to:

• Category N (not symptomatic): no signs or symptoms considered to be the result of HIV infection or only one of the conditions listed in Category A.
• Category A (mildly symptomatic): two or more of the conditions listed below but none of the conditions listed in Categories B and C.
• Lymphadenopathy larger than 0.5 cm at more than two sites.
• Hepatomegaly.
• Splenomegaly.
• Dermatitis.
• Parotitis.
• Recurrent or persistent upper respiratory infection, sinusitis or otitis media.
• Category B (moderately symptomatic): symptomatic conditions other than those listed for Category A or C that are attributed to HIV infection. Examples of conditions in clinical Category B include but are not limited to:
• Anaemia, neutropenia or thrombocytopenia persisting for longer than 30 days.
• Bacterial meningitis, pneumonia, or sepsis.
• Persistent oropharyngeal candidiasis in children less than six months of age.
• Cardiomyopathy.
• Cytomegalovirus infection, with onset before one month of age.
• Diarrhoea, recurrent or chronic.
• Hepatitis.
• Recurrent herpes simplex virus stomatitis.
• Herpes simplex virus bronchitis, pneumonitis, or oesophagitis with onset before one month of age.
• Herpes zoster involving at least two distinct episodes or more than one skin area.
• Leiomyosarcoma.
• Lymphoid interstitial pneumonia or pulmonary lymphoid hyperplasia complex.
• Nephropathy.
• Nocardiosis.
• Persistent fever lasting longer than one month.
• Toxoplasmosis, onset before one month of age.
• Disseminated varicella.
• Category C (severely symptomatic): any condition listed in the 1987 surveillance case definition for AIDS, with the exception of lymphoid interstitial pneumonia.