AIDS

The term AIDS applies to the most advanced stages of HIV infection. Official criteria for the definition of AIDS are developed by the CDC in Atlanta, Ga., which is responsible for tracking the spread of AIDS in the United States.

In 1993, CDC revised its definition of AIDS to include all HIV-infected people who have fewer than 200 CD4+ T cells. (Healthy adults usually have CD4+ T-cell counts of 1,000 or more.) In addition, the definition includes 26 clinical conditions that affect people with advanced HIV disease. Most AIDS-defining conditions are opportunistic infections, which rarely cause harm in healthy individuals. In people with AIDS, however, these infections are often severe and sometimes fatal because the immune system is so ravaged by HIV that the body cannot fight off certain bacteria, viruses and other microbes.

Opportunistic infections common in people with AIDS cause such symptoms as coughing, shortness of breath, seizures, mental symptoms such as confusion and forgetfulness, severe and persistent diarrhea, fever, vision loss, severe headaches, weight loss, extreme fatigue, nausea, vomiting, lack of coordination, coma, abdominal cramps, or difficult or painful swallowing.

Although children with AIDS are susceptible to the same opportunistic infections as adults with the disease, they also experience severe forms of the bacterial infections to which children are especially prone, such as conjunctivitis (pink eye), ear infections and tonsillitis.

People with AIDS are particularly prone to developing various cancers, especially those caused by viruses such as Kaposi's sarcoma and cervical cancer, or cancers of the immune system known as lymphomas. These cancers are usually more aggressive and difficult to treat in people with AIDS. Hallmarks of Kaposi's sarcoma in light-skinned people are round brown, reddish or purple spots that develop in the skin or in the mouth. In dark-skinned people, the spots are more pigmented.

During the course of HIV infection, most people experience a gradual decline in the number of CD4+ T cells, although some individuals may have abrupt and dramatic drops in their CD4+ T-cell counts. A person with CD4+ T cells above 200 may experience some of the early symptoms of HIV disease. Others may have no symptoms even though their CD4+ T-cell count is below 200.

Many people are so debilitated by the symptoms of AIDS that they are unable to hold steady employment or do household chores. Other people with AIDS may experience phases of intense life-threatening illness followed by phases of normal functioning.

A small number of people (less than 50) initially infected with HIV 10 or more years ago have not developed symptoms of AIDS. Scientists are trying to determine what factors may account for their lack of progression to AIDS, such as particular characteristics of their immune systems, or whether they were infected with a less aggressive strain of the virus or if their genetic make-up may protect them from the effects of HIV. Scientists hope that understanding the body’s natural method of control may lead to ideas for protective HIV vaccines and use of vaccines to prevent disease progression