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The natural history and clinical features of HIV infection in adults and adolescents

John G Bartlett, MD
Section Editor
Martin S Hirsch, MD
Deputy Editor
Howard Libman, MD, FACP


Since the original description in 1981 of an unusual cluster of cases of Pneumocystis carinii pneumonia and Kaposi sarcoma in previously healthy men who have sex with men, substantial advances in our understanding of the acquired immunodeficiency syndrome (AIDS) have been achieved. The identification of a cytopathic retrovirus in 1983 and development of a diagnostic serologic test for human immunodeficiency virus (HIV) in 1985 have served as the basis for developing improvements in diagnosis.

In addition, therapy was dramatically altered with the introduction of antiretroviral drugs in 1987 and revolutionized by combination antiretroviral therapy (ART) in 1996. In the three years following the introduction of ART, mortality, AIDS, AIDS-defining diagnoses, and hospitalizations all decreased 60 to 80 percent. The EuroSIDA study, comparing this early ART period with pre-ART and later ART (1998 to 2002) treatment periods, found a sustained decrease in mortality and progression to AIDS with ongoing ART [1]. Despite the absence of a cure, the natural history of the disease was radically changed and patients with HIV infection without other significant comorbidities who are treated appropriately can expect to have a life expectancy the same as the general population [2].

Despite these advances, it is still useful to review the natural history of HIV infection without ART and the classification of disease. Although modified from the initial case definition, the newer Centers for Disease Control and Prevention (CDC) classification system remains the cornerstone for diagnosing HIV and AIDS.

This topic reviews the case definition, stages, and natural history of HIV infection. The epidemiology of HIV infection, factors that influence the natural history of HIV infection, and the impact of ART on the natural history are discussed elsewhere. (See "Global epidemiology of HIV infection" and "Factors affecting HIV progression" and "The impact of antiretroviral therapy on morbidity and mortality of HIV infection in resource-limited settings".)


Clarification of the case definition of HIV infection is important for surveillance and public health purposes. Organizations such as the Centers for Disease Control and Prevention (CDC) in the United States and the World Health Organization (WHO) have established case definitions to standardize the description of HIV infection cases. Although they reflect the clinical diagnostic evaluation for HIV infection, these case definitions are not intended to serve as the bases for clinical decisions in individual patients. The clinical diagnosis of HIV infection is discussed in detail elsewhere. (See "Screening and diagnostic testing for HIV infection", section on 'Testing algorithm'.)

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Literature review current through: Nov 2017. | This topic last updated: Aug 29, 2017.
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