Where Did HIV Come From?

The origin of HIV has been a topic for debate and scientific research for many years since the first diagnosis of the virus in the 80s. There is extensive evidence out there illustrating the circumstances that led to the HIV/AIDS pandemic it is today.

We have two types of lentiviruses causing AIDS; human immunodeficiency viruses type 1 and 2 (HIV-1 and HIV-2). According to scientific revelations, both viruses resulted from multiple cross-species transmission of simian immunodeficiency viruses (SIVs) found in African primates. However, such viruses spread to human only to a limited extent where one transmission event involving a type of SIV affecting chimpanzees in southern parts of Cameroon and Congo- SIVcpz gave rise to HIV-1 which is the primary cause of AIDS. Scientists believe, it is this SIVcpz virus that was transmitted to humans before mutating to HIV-1 upon eating chimpanzee meat and came into contact with the primates’ blood.

Slowly but steadily, the virus spread through Africa before finally getting to other parts of the world.

How is HIV linked to SIV?

Both viruses are lentiviruses that attack the immune system of host bodies. For HIV, it attacks the immune system of the human beings while SIV affects the immune system of apes and monkeys. Further research reveals that the two are closely related and have many similarities. While HIV-1 is closely related to a strain of SIV n chimpanzees, HIV-2 is related to another strain of SIV in sooty mangabeys.

Did HIV originate from monkeys?

In the late 90s, a strain of SIV was found in chimpanzees by researchers and proved to be almost identical to the HIV in human beings. The researchers, upon conducting several tests, came to the conclusion that chimpanzees must have been the source of HIV-1 and that the virus must have crossed to humans at some point in time from the chimpanzees. Digging deeper, the researchers discovered that the chimpanzees had hunted down other smaller species of monkeys and eaten them. The smaller monkeys infected the chimpanzees with two other strains of SIV which joined together to form a third strain of virus-SIVcpz that was later transmitted to other chimps. The virus was then proved to infect humans.

The crossing of HIV from chimpanzees to humans

The hunter-theory is the most commonly accepted today pointing out that the virus crossed to humans as a result of consuming chimpanzee meat and the primates’ blood getting into contact with the hunters through open wounds or cuts.

The researchers indicate that there are four main strains of HIV-M, N, O, and P each having a slightly different genetic makeup. This explains the reason why there are many strains of HIV-1 in humans considering a different strain of SIV could cross to a human each time they consumed the meat.

The most studied and researched strain is HIV-1 group M, due to its vast spread across the world and responsible for the majority of HIV infections.

How HIV-2 crossed to humans

HIV-2 is believed to have come from SIVsmm in sooty mangabey monkeys instead of chimpanzees. It is also believed to have passed to humans in the same way of consuming the primates’ meat. This strain of HIV is less infectious compared to HIV-1 hence explaining why it is rare and only found in a few West African countries such as Nigeria, Mali, Mauritania and Sierra Leone.

Where and when was the first time HIV was detected in Humans?

Some of the earliest samples of HIV have been studies to give a clue on where and when the virus appeared first. The first verified case points at the Democratic Republic of Congo where a blood sample of a man taken in 1959 was diagnosed to have the virus. Earlier cases with specific death patterns from common opportunistic disease also suggest that the HIV was responsible. However, the very first blood sample that verifies HIV infection is the one that was taken in 1959.

Is Africa the origin of HIV?

A “family tree” ancestry of HIV transmission created by scientists traces back the origin of HIV to be Africa. According to their studies, the first transmission of SIV in primates to HIV in humans took place in the early 1920s in Kinshasa, Democratic Republic of Congo. The area is also known to have the most genetic diversity in strains of HIV more than any other in the world. This may be a clear reflection of the number of times SIV was passed on to humans. Besides, many cases of AIDs were first recorded here.

Due to a well-developed transport network around the area including roads, river, and railway, it became easy for the virus to spread to several other areas and regions. Besides, there was also a growing sex trade around the time HIV started spreading. With more immigrants and sex trade, the virus quickly spread fast to other areas with only ten years later the virus reaching Brazzaville which is more than 120 km away from Kinshasa.

Surprisingly, by early 80s when HIV became common across the world, half of all infections in DR Congo were outside Kinshasa which points out how fast the epidemic grew.

HIV in the USA

In the 1980s, people entirely became aware of the HIV pandemic and officially labeled as a deadly condition all over the world. By this time the spread was slow, and few cases of rare diseases were being reported among gay men in the US cities like Kaposi’s sarcoma and lung infections, but no one knew the reason why the opportunistic diseases were spreading until later when it was concluded that it was an infectious disease that was causing them.

At first, the condition was viewed as a gay disease, and people gave it various names including gay compromise syndrome until 1982 when scientists discovered that condition was spreading among other populations like injection drug users especially heroin users and hemophiliacs. Later in 1983, HIV was isolated and identified by researchers in France- the Pasteur Institute who named the virus Lymphadenopathy-Associated Virus (LAV). The virus was confirmed to be the cause for AIDS. Other researchers working at the USA National Cancer Institute also isolated the virus and named it HTLV-III. It is only later that the two studies were acknowledged to be the same thing.

In the same year, the Centers for Disease Control and Prevention listed all groups of people at risk including people injecting drugs, partners of people with the virus, hemophiliacs and people that had been to Haiti the most recent time. Due to immeasurable panic and lack of knowledge, people began group people and related them to HIV. Then came up the Four-H-Club: Homosexuals, Hemophiliacs, Haitians and Heroin addicts. This even worsened as stigmatization went high before more research was conducted and more information put out there regarding the “deadly” virus.

References:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3234451/

https://www.ncbi.nlm.nih.gov/pubmed/20847261

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3234451/

https://www.ncbi.nlm.nih.gov/pubmed/9989410

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC191547/

http://www.sciencemag.org/news/1998/02/oldest-surviving-hiv-virus-tells-all

http://www.sciencemag.org/content/346/6205/56.abstract

https://www.bbc.co.uk/news/health-29442642

https://www.ncbi.nlm.nih.gov/pubmed/6116083

https://www.cdc.gov/mmwr/preview/mmwrhtml/00001126.htm

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