The Origins of HIV







Since the AIDS epidemic first emerged in the early 1980s, people have speculated about the origin of the disease. In the following decades, numerous theories about the origins of HIV emerged. Many of these theories were quickly disproved, but a few of the theories remain popular today with both the scientific community and the public.

The Hunter Theory of HIV Origin

The most commonly accepted theory of the development of HIV is called the “hunter” theory. In this theory, Simian Immunodeficiency Virus (SIV), a virus similar to HIV that infects other primates, was transferred when humans killed chimps for food. The virus entered their system either through ingestion of infected meat or by getting infected chimp blood into their own blood stream.

Strains of SIV matching both HIV-1 and HIV-2, the two strains of HIV, have been found in chimpanzees and monkeys living in Africa. Other similar viruses have been found to jump between species in a process called zoonosis.

Oral Polio Vaccine Theory

A second theory contends that HIV was transferred to people in Africa via the oral polio vaccine called Chat. A book titled The River, by journalist Edward Hooper, traces the use of the vaccine in the Congo, Rwanda, and Uganda in the late 1950s. This thoroughly researched book documents the process that Hooper believes created the AIDS epidemic.

Oral polio vaccine was cultivated in kidney cells taken from chimpanzees. Hooper contended that the vaccine used was grown in SIV infected cells. In 2000, the original manufacturer of the vaccine, the Wistar Institute in Philadelphia, found vials of the same vaccine that was administered in the 1950s. They announced that there was no HIV or SIV in the vaccine. Later, they released information stating that the cells used to grow the vaccine were from macaque monkeys, a primate that cannot be infected with SIV or HIV.

If the oral polio vaccine theory were true, scientist would expect to see just one group of HIV. Since there are a range of groups in existence, evidence suggests that the transferal from apes to humans must have occurred in another way. This same evidence also suggests that HIV was in existence before the polio vaccine was ever given.

Conspiracy Theories of HIV Origin

A survey carried out in the United States by the Centers for Disease Control and Prevention showed that a significant number of individuals believe that HIV is a man-made disease designed to wipe out large numbers of African-Americans and homosexuals. The theory is that the virus was developed by the US Federal Special Cancer Virus Program. The virus was supposedly spread throughout the population using the smallpox and Hepatitis B vaccines.

Historical and scientific evidence do not support this theory since HIV has been traced back as far as 1959, twenty-three years before the Hepatitis B vaccine was developed. There is also an overwhelming amount of evidence that shows that HIV is related to SIV.

So, now another opinion:

Where did HIV originate? First, HIV-2 is very closely related to SIV, the simian immune virus, found in sooty mangabeys. Baboons can be infected with HIV-1 and they can also suffer from a version of SIV. At the 6th American Conference on Retroviruses and Opportunistic Infections held in Chicago from January 31-February 4, 1999, one of the keynote papers delivered by Beatrice Hahn on the first day presented evidence that HIV-1 is likely to have originated in West African chimpanzees of the species Pan troglodytes troglodytes. HIV could have been transferred from monkeys because they have long been kept as pets and used for food. When hunting monkeys it is not unusual for both the hunter and the hunted to exchange blood during capture. Currently there is a large market in "bush meat" obtained from monkeys. This does not bode well because there may well be continuing transfer of the disease from monkeys to humans.

The earliest fully documented case of HIV dates back to 1959. A Congolese man's blood sample from a medical study was preserved, found, and then analyzed in 1998. It was verified that he had been HIV+. Other suspected, but unverified because of the lack of either blood or tissue samples, cases date back as early as 1934. On February 1, 2000, M. Korber, et al. reported the results of a phylogenetic statistical analysis of the evolution of the retroviral genome of HIV using complex mathematical models allowing for both constant and variable rates of evolution. Her group's analysis required the use of supercomputers to backtrack the evolution to its source from monkeys. The most reliable time of origin in humans is somewhere around 1930 (a 95% confidence interval extends from 1910 to 1950). Several naysayers have claimed that the disease originated from the use of African green monkey kidneys to cultivate poliovirus in the late 1950's and early 1960's. This analysis finds that argument to be a very low probability event, hence quite unlikely.

The first recorded cases in the U.S. occurred in New York City in 1952, 1959, and 1979. The cases from the 1950s were both males with PCP and other unusual infections. The first reported cases were those in the June 5, 1981 MMWR mentioned earlier. The watershed event that brought the disease into full view of the public eye was the announcement that the (thought to be very macho) film star Rock Hudson had the disease. (Even after he had been diagnosed with AIDS, he continued cruising the gay bars and did not notify any of his sexual partners of his HIV status.)



Research shows HIV's ancestor millions of years older than believed.........Findings open a new avenue

An ancient predecessor to the virus that causes Aids evolved in wild primates many millions of years earlier than previously believed, according to research published yesterday by the Stanford University School of Medicine.

The findings open a critical new avenue in the quest to understand the origins of the human immunodeficiency virus, or HIV, which unleashed a pandemic that since 1981 has claimed more than 25 million lives worldwide, and threatens millions more.

The discovery also bolsters scientific hunches that HIV-like viruses may be more broadly distributed among primates and other wildlife than previously thought, posing a potential risk for humans in close contact with these animals. Primates in Africa passed on the two strains of HIV circulating among humans, scientists are convinced.

"It points to the direction for future research, that we need to establish how widespread these viruses are," said Robert Gifford, an infectious disease researcher with Stanford, and lead author of the study.

Gifford and his colleagues studied gray mouse lemurs, squirrel-sized, saucer-eyed primates found in Madagascar.

They found that the lemur genomes they studied carried lentiviruses, which are among a family of viruses that include HIV. Lentiviruses have been intensely studied since the emergence of Aids.

While the discovery of lentiviruses in lemurs surprised the researchers, what especially stunned them was the realisation that lemurs must have carried the virus for at least 14m years.

That was the last time a land bridge might have existed between the island and mainland Africa, providing an opportunity for another species infected with the virus to pass it to the geographically isolated animals, which are native only to Madagascar.

At the outside, lemurs may have carried the virus for as long as 85m years, when the primate family that includes lemurs split from the evolutionary branch that gave rise to monkeys, apes and humans. The only other way lemurs could have acquired lentiviruses would have required mammals such as infected bats to wing their way across the 400km span of ocean between Madagascar and Africa – which the scientists consider unlikely.

The findings upend long-held beliefs about how long primates have carried HIV-like viruses, and how recently these viruses evolved. "There was a generally accepted maximum of a million years," Gifford said. "But many people thought it might be less than that."

Honing in on how long species carrying lentiviruses have harboured the pathogens helps scientists understand how they spread and evolve in wild populations, and the prevalence of biological defences against them. Certain species of primates, such as mandrills, sooty mangabeys and green monkeys, harbour the viruses without getting ill.

That knowledge could be used to protect humans from transmission of other HIV-like viruses still confined to wildlife. It could also help drug development by pinpointing features of the virus that remain fixed through its evolution. These fixed features may prove critical for normal functioning of the virus, and provide a target for new Aids drugs.

The HIV-2 strain is widely accepted to have been passed from sooty mangabeys in west Africa to humans, probably bushmeat hunters or those keeping the primates as pets, or both. Scientists believe HIV-1 was passed from chimpanzees to humans.

"There's an imperative to try to establish from these findings what the distribution of lentiviruses is, what the routes of transmission are, and the time frame," Gifford said.





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