The federal Centers for Disease Control divides patients infected by HIV, the virus that causes AIDS, into four categories.

GROUP I:

Includes people with temporary signs and symptoms that often appear shortly after initial infection and then subside.

GROUP II:

Includes people who are infected with the virus but show no signs or symptoms. Laboratory studies indicate that many people in this group have subtle abnormalities in their immune system.

GROUP III:

Includes infected people who have chronically swollen lymph nodes but who have none of the other signs of AIDS. People in this group can be placed into more specific categories based on the results of tests that measure the strength of the immune system.

GROUP IV:

People in this group display clinical symptoms associated with AIDS. The classification has five subgroups, and patients can be assigned to one or more based on their clinical condition.

One subgroup applies to people who have fevers or diarrhea lasting for more than one month, involuntary weight loss of more than 10 percent and the absence of other illness.

A second applies to those with neurological disease caused by HIV.

A third encompasses secondary infections such as toxoplasmosis and pneumocystis carinii pneumonia.

A fourth applies to those with cancers.

The last refers to other conditions of HIV infection such as other rare types of pneumonia.