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What Is HIV Pandemic’s Origin?

Wise Chimpanzee

Image credit: George, “Wise Chimpanzee,” via Flickr. CC BY-NC-SA 2.0

As it is generally accepted that that HIV has originated from the non-human primates, but the reason why HIV has caused the world-wide pandemic in humans is unknown for a quite long time. And now, in order to analyze hundreds of genetic sequences of HIV, a group of scientists, by application of the sophisticated statistical techniques, has followed the virus’ footsteps to present a clear clue about the development of HIV globally. According to their study, they made a confirmative conclusion that Kinshasa, the capital of the Democratic Republic of the Congo (DRC), was the starting point of the HIV pandemic. In addition, the scientists had mapped out what occurred next for the first time. The result of their research has been publicly released in Science.

HIV was closely linked with the simian immunodeficiency viruses (SIVs), which could that naturally infect so many different non-human primate species. Such viruses were in fact transmitted to humans at least 13 times, however just in one case; they had resulted in the HIV pandemic, which gave rise to the group having the most prevalent strains of HIV—HIV-1 group M. That was blamed for nearly ninety-percent of infections all over the world.

What would happen if the group M was separated from other groups containing less successful strains? One suggestion was that these viruses were much powerful in running away from the host’s immune system. However, the new research paid more attention to the role of other important factors like transport and social changes that were usually ignored before.

During their study, the scientists from Oxford University and University of Leuven were engaged in analysis of the genomes of viruses from 814 infected individuals who had lived in central Africa from 1959 to the late 1980s. Additionally, they also targeted at the earliest known HIV-1 infection, also called ZR59, which was discovered in a male living in Kinshasa in 1959.

In comparison of the sequences over the time, the researchers had succeeded in identifying viral mutation rates as well as the rate of evolution. Based on them, scientists were capable of tracing backward and mapping out a viral timeline, covering the pre-epidemic days.

The previous studies showed that the common ancestor of group M appeared in the period from 1884 to 1924 and it originated from a chimpanzee and then transmitted to a human who lived in the south eastern part of Cameroon. Most possibly, it came from a butcher or a hunter who happened to contact with infected blood. It was likely that the virus was first circulated among the local people and then it found its presence at Kinshasa around 1920.

At that time, the virus started to spread quickly owing to the building project of a new railway. So in this way, the project attracted many local workers to the region, but on the other hand, it also mad it possible for the infected people to move to other big cities in central Africa. By the end of the 1940s, more than one million people had started their journeys on this railway from Kinshasa to other areas every year, thus helping build up more secondary transmission regions.

During the same period of time, another group of viruses, called as Group O, began to spread in Cameroon at similar rates. However after the 1960s, the Group M was at its explosion stage, which in the opinion of scientists was possibly attributed to the independence DRC in 1960, an event that was so closely associated with great cultural and social changes. Unfortunately, the booming sex industry and more public health campaigns helped the wide use of contaminated needles, thus HIV had spread like wildfire.

Although scientists were not sure about the fact that viral differences were keys to the success of group M, they were considering it should the good example of “right place, right time.”

Source: Oxford UniversityScienceNew ScientistNational Geographic

Journal reference: Faria, Nuno R., et al. “The early spread and epidemic ignition of HIV-1 in human populations.” Science 346.6205 (2014): 56-61.