There are two methods or systems used to classify adults who are infected with HIV—this classification guides the treatment plans. The first system is based on the CD4+ cell count, which measures the effects of HIV on the immune system. The second system is based on symptoms (clinical categories). Each person who has HIV is classified in both ways.

CD4+ categories

• Category 1: More than 500 CD4+ cells per microliter (mcL) of blood
• Category 2: 200 to 499 CD4+ cells/mcL
• Category 3: Fewer than 200 CD4+ cells/mcL

Generally, the higher the CD4+ count, the less likely it is that opportunistic diseases will occur. Most people who have untreated HIV experience a gradual drop in the number of CD4+ cells. Each person responds uniquely to this decline.

Clinical categories

Category A includes one or more of the conditions listed below in an adult who has a documented HIV infection:

• Acute (primary) retroviral infection or a history of acute HIV infection
• HIV infection without symptoms (asymptomatic)
• Enlarged lymph nodes (lymphadenopathy). Often the first symptom of HIV infection is swollen lymph nodes in the armpits, neck, or groin.

In order for a person to fit into category A, conditions that are listed in categories B and C must not have occurred.

Category B includes symptoms of HIV infection or symptoms that indicate an impaired immune system. It also includes other conditions that need medical treatment, but both the condition and the treatment may be more complicated because of the HIV infection.

Examples of conditions in clinical category B include:

• Yeast infection of the mouth (thrush) or persistent vaginal yeast infection.
• Abnormal Pap test (moderate to severe cervical dysplasia).
• Fever of 101.4°F (38.56°C).
• Diarrhea that lasts longer than 1 month.
• Thick sores on the sides of the tongue (hairy leukoplakia).
• Shingles (herpes zoster).
• Listeriosis (a disease caused by the bacterium Listeria monocytogenes that often leads to meningitis).
• Pelvic inflammatory disease (PID).
• Loss of or altered feeling in the hands and feet (peripheral neuropathy).

In order for a person to fit into category B, conditions that are listed in category C must not have occurred.

Category C (AIDS-indicator condition) includes opportunistic infections or cancers that rarely occur in healthy people. These infections can be fatal because the immune system is too weak to fight infections. Examples of conditions in clinical category C include but are not limited to:

• Pneumocystispneumonia (PCP).
• Cancer of the lymphatic system (lymphoma).
• Tuberculosis.
• Cancer of the cervix.
• Kaposi's sarcoma in a person younger than 60.
• Cytomegalovirus infection.
• Toxoplasmosis infection of the brain.
• Mycobacterium avium complex infection.

When a person's condition becomes more serious, his or her category may be changed to a more serious one (for example, moved from category A to category B). The category is never changed to a lesser one (such as from category C to category B), even if the person's condition improves.