Thursday 16 March 2017

HIV/AIDS: The Past, Present and Future





Human immune deficiency virus (HIV) is closely related to the simian immunodeficiency virus which is found in monkeys and apes. HIV-I is closely related to the strains of SIV found in chimpanzees, and HIV-II is closely related to the strains of SIV found in the sooty mangabeys. In 1999 some scientists found a strain of SIV ( called SIVcpz) in chimpanzees that was closely related to HIV-I in humans. It was then concluded that this proved that chimpanzees were the source of HIV-I and had crossed species to humans at some point in time. Furthermore it was thought that these chimpanzees got the SIV virus by eating two smaller monkeys (red-capped mangabeys and greater spot nosed monkeys) and became infected with two strains of SIV. These two strains joined together to form the SIVcpz strain which has the ability to infect humans. This was followed by the concept of the hunter who ate these chimpanzees and became infected or the viruses were able to access the hunter through wounds and cuts. Ocassionally the hunter would be able to ‘fight’ off this SIV, but sometimes they were able to survive in humans as HIV. 

HIV-II comes from SIVsmm in sooty mangabey monkeys rather than chimpanzees. The crossover to humans is believed to have happened in a similar way (through the killing and consumption of monkey meat). It is far rarer, and less infectious than HIV-1. As a result, it infects far fewer people, and is mainly found in a few countries in West Africa like Mali, Mauritania, Nigeria and Sierra Leone. There are four groups of HIV strains M,N,O,P with M being the most common with nine subtypes (A-D,F-H,J,K). There are so many strains because in the attempt to enter and adapt to survive within the human system the SIV had to evolve into several strains the most successful being able to survive the new environment.

Researchers have come to the conclusion that this “zoonotic” infection of humans with this virus started around 1920 in the Democratic Republic of Congo. The same area is known for having the most genetic diversity in HIV strains than anywhere else, reflecting the number of different times SIV was passed to humans. Many of the first cases of AIDS were recorded there too. The extensive transport routes in that part including the railways, rivers and road networks together with the high migrant population and growing sex trade all supported the spread of the HIV virus. The lack of transport routes in the north and east of the country accounted for the lower reports of infections from these regions at the time. By 1980, half of all infections in DR Congo were in locations outside of the Kinshasa area, reflecting the growing epidemic. 

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