Staging, classification, and natural history of HIV disease

This chapter provides some historical background to the development of HIV disease-staging and classification systems. The illness (AIDS) was described before the discovery of HIV, the causative agent. The Centres for Disease Control and Prevention (CDC) devised a classification system, revised in 1993, based on clinical features, AIDS-defining illnesses, and CD4 counts. The revised WHO Clinical Staging of HIV/AIDS for Adults and Adolescents is based on clinical progression, and is used in 3rd world countries and as a research tool. This chapter provides description of the natural history of untreated HIV infection. Without treatment, HIV is invariably fatal, but the course is variable depending on CD4 count, host factors, and the development of conditions such as opportunistic infections and malignancies.