What Is the Origin of HIV?

Genetic Research Pinponts the Virologic "Jump" of HIV from Monkey to Man

Electron micrograph of HIV virions (in yellow) budding from an infected CD4+ T-cell. Photo credit: National Institute of Allergies and Infectious Diseases (NIAID)

It is largely been accepted that HIV-1 originated as a result of the hybridization (or mixing) of two strains of simian immunodeficiency virus (SIV)—one from the red-capped macabey and the other from the greater-spot nosed monkey. The hybridized SIV was then believed to have infected Pan troglodytes troglydytes chimpanzee in Central Africa, which was then passed to humans through blood-to-blood exposure and/or the consumption of bush meat.

Zoonotic diseases—those that jump from animals to humans—are not an uncommon phenomena, with increasing genetic evidence suggesting that even measles, smallpox and diptheria may be a result of cross-species infection. Salmonellosis, a bacterial infection which can progress to an AIDS-defining condition, is a prime example, most often the result of ingesting contaminated meat, eggs or dairy products.

New research from investigators at Oxford University has concluded that the “jump” is likely to have occurred in Kinshasa, the capital of the Democratic Republic of Congo (DRC), somewhere in the 1920s and was the source of pandemic  virus we know today.

Genetic  Sequencing Confirms Geographical Center

In order to determine this, the scientists compared the genetic diversity of viruses found in the Congo Basin, including the DRC and Cameroon. What were they able to determine was that, using the genetic clues and historical data, the outbreak did not start in Cameroon as previously thought, but was a result of the spread of the virus between Kinshasa and Cameroon as result of river trade.

The investigators ultimately confirmed that virus found in Kinshasa exhibited more HIV-1 genetic diversity than anywhere else—resulting from the spread of the rapidly mutating virus from person to person—as well as the oldest known HIV-1 genetic sequences.

From the 1920s to 1950s, rapid urbanization and the development of railways made Kinshasa a transport capital, thereby allowing the spread of HIV-1 throughout the country and soon after to East and Southern Africa.

 

Between the 1950s and 60s, the use of unsterilized hypodermic needles in sexually transmissible diseases clinics and the growth of commercial sex trade were among the factors for the rapid of spread of the viruses, particularly in mining communities where there was (and continues to be) a high migratory workforce.

It was not until 1981 that the first cases of AIDS were identified in the U.S., with  the isolation of HIV-1  virus made two years later in 1983. Today, as a result of the pandemic, nearly 75 million infections have occurred, resulting in over 30 million deaths.

As of 2015, over 36 million people are known to be infected with HIV worldwide.

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Sources:

Gao, F.; Bailes, E.; Chen, Y.; et al. "Origin of HIV-1 in the chimpanzee Pan troglodytes troglodytes." Nature. February 4, 1999; 397(6718): 385-386.

Bedford, M.; Ward, A.; Tatem, J.; Sousa, et al. "The early spread and epidemic ignition of HIV-1 in human populations." Science. October 3, 2014; 346(6205):56-61.

United Nations Programme on HIV/AIDS (UNAIDS). "Global Reports – UNAIDS report on the global AID epidemic 2013." 2013; Geneva, Switzerland.

Centers for Disease Control and Prevention (CDC). "Pneumocystis pneumonia – Los Angeles." Morbidity and Mortality Weekly Report (MMWR). 1981; Atlanta, Georgia.

Barré-Sinoussi, F.; Chermann, J.; Rey, F.; et al. "Isolation of a T-lymphotropic retrovirus from a patient at risk for acquired immune deficiency syndrome (AIDS) ." Science. May 20, 1983, 220(4599):868-871.

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