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Global epidemiology of HIV infection

Thomas C Quinn, MD
Section Editor
John A Bartlett, MD
Deputy Editor
Allyson Bloom, MD


The acquired immunodeficiency syndrome (AIDS) was first recognized among homosexual men in the United States in 1981 [1,2]. While initially limited, infection with the human immunodeficiency virus (HIV) has literally exploded over the past three decades to become the worst epidemic of the twentieth century. With more than 35 million fatalities, the AIDS epidemic now ranks alongside the influenza pandemic of the early 1900s and the Bubonic plague of the 14th century in terms of fatalities [3]. The impact of this disease on human suffering, cultures, demographics, economics, and even politics has been felt in nearly every society across the globe.

The initial optimism that followed the discovery of HIV, the development of diagnostic assays to help monitor the epidemic, the prophylaxis of opportunistic infections, the identification of effective antiretroviral drugs, and the prevention of perinatal transmission, has been tempered by the stark reality and magnitude of the global HIV pandemic. The epidemic continues to spread relentlessly into new areas and to consolidate in many other locations. In some countries in sub-Saharan Africa, the AIDS epidemic had caused a dramatic decline on life expectancy that may only now be rebounding with access to antiretrovirals.

This topic reviews worldwide statistics on the global HIV epidemic, modes of transmission, and the introduction of antiretroviral therapy (ART) into resource-limited settings. Updated information on global statistics is available on the Joint United Nations Programme on HIV/AIDS (UNAIDS) and on the United States Centers for Disease Control and Prevention (CDC) websites: www.unaids.org and www.cdc.gov, respectively. The clinical impact of ART on morbidity and mortality and the prevention of HIV are discussed in detail elsewhere. (See "The impact of antiretroviral therapy on morbidity and mortality of HIV infection in resource-limited settings" and "HIV infection: Risk factors and prevention strategies" and "When to initiate antiretroviral therapy in HIV-infected patients", section on 'Benefits of antiretroviral therapy'.)


While AIDS was only recognized in 1981, molecular phylogenetic studies indicate that HIV was present in central Africa since the early 1900s, likely in localized populations [4]. The current pandemic may have emerged from these populations in the mid-1900s with improved access to transport and other societal changes [5].

Zoonotic transmission — Molecular phylogenetic studies suggest that HIV evolved from a lentivirus, simian immunodeficiency virus (SIV), which has been found in some subspecies of monkeys from Bioko (an island off the East African coast) and some subspecies of chimpanzees in the Cameroon [6,7]. Researchers believe that all the SIV strains infecting primates across Africa diverged from a common ancestor between 32,000 and 78,000 years ago [7].

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Literature review current through: Nov 2017. | This topic last updated: Aug 24, 2016.
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