The term AIDS applies to the most advanced stages of HIV infection. Generally speaking AIDS develops in those people who are not taking HIV medication, usually because they are unaware of their infection. But AIDS can develop on treatment, because the virus has developed drug resistance.
The Centers for Disease Control (CDC) in Atlanta, USA, develops official criteria for the definition of AIDS. Their definition includes all HIV-infected people who have fewer than 200 CD4 T cells per microlitre of blood (i.e. less than 0.2 x 109/L). (Healthy adults usually have CD4 T-cell counts of 1,000 or more.) In addition, the definition includes 26 opportunistic infections that affect people who have advanced HIV disease.
Most of these conditions are called opportunistic infections because they rarely cause medical problems in healthy people. In people with AIDS, these infections are often severe and sometimes fatal because the immune system is so damaged by HIV that the body cannot fight off certain bacteria, viruses, fungi, parasites, and other microbes.
Opportunistic infections common in people with AIDS cause symptoms such as:
- coughing and shortness of breath
- seizures and lack of coordination
- difficult or painful swallowing
- mental symptoms such as confusion and forgetfulness
- severe and persistent diarrhoea
- vision loss
- feeling sick, abdominal cramps, and vomiting
- weight loss and extreme fatigue
- severe headaches, and
Last Review Date: April 18, 2012