* YOU BEEN SNAP* YAKULETEA MACHACHE KUHUSU HILI GONJWA MBAYA MNO" JE NI KWELI HIV -AIDS ILITOKEA AFRICA ? SOMA UJUE ILIKOTOKEA NA HOW COME " GOD BLESS THE WORLD NA MADAKITARI WAWEZE KUTUPATIA TIBA YAKE ULIMWENGUNI .NA R.I.P. HAPPY PEOPLE WOTE MLOKUFA KWA GONJWA HILI NA HATA KWA KIFO CHOCHOTE" TULIZALIWA SABABU YA KUISHI AU " MBUTA NANGA!!

origin of AIDS and HIV has puzzled scientists ever since the illness first came to light in the early 1980s. For over twenty years it has been the subject of fierce debate and the cause of countless arguments, with everything from a promiscuous flight attendant to a suspect vaccine programme being blamed. So what is the truth? Just where did AIDS come from?
The first recognised cases of AIDS occurred in the USA in the early 1980s A number of gay men in New York and California suddenly began to develop rare opportunistic infections and cancers that seemed stubbornly resistant to any treatment. At this time, AIDS did not yet have a name, but it quickly became obvious that all the men were suffering from a common syndrome.
The discovery of HIV, the Human Immunodeficiency Virus, was made soon after. While some were initially resistant to acknowledge the connection (and indeed some remain so today), there is now clear evidence to prove that HIV causes AIDS. So, in order to find the source of AIDS, it is necessary to look for the origin of HIV, and find out how, when and where HIV first began to cause disease in humans.

back to topHow?

What type of virus is HIV?

HIV is a lentivirus, and like all viruses of this type, it attacks the immune system. Lentiviruses are in turn part of a larger group of viruses known as retroviruses. The name 'lentivirus' literally means 'slow virus' because they take such a long time to produce any adverse effects in the body. They have been found in a number of different animals, including cats, sheep, horses and cattle. However, the most interesting lentivirus in terms of the investigation into the origins of HIV is the Simian Immunodeficiency Virus (SIV) that affects monkeys, which is believed to be at least 32,000 years old.¹

So did HIV come from an SIV?   

It is now thought that HIV came from a similar virus found in chimpanzees.

It is now generally accepted that HIV is a descendant of a Simian Immunodeficiency Virus because certain strains of SIVs bear a very close resemblance to HIV-1 and HIV-2, the two types of HIV.
HIV-2 for example corresponds to SIVsm, a strain of the Simian Immunodeficiency Virus found in the sooty mangabey (also known as the White-collared monkey), which is indigenous to western Africa.
The more virulent, pandemic strain of HIV, namely HIV-1, was until recently more difficult to place. Until 1999, the closest counterpart that had been identified was SIVcpz, the SIV found in chimpanzees. However, this virus still had certain significant differences from HIV.

What happened in 1999?

In February 1999 a group of researchers from the University of Alabama² announced that they had found a type of SIVcpz that was almost identical to HIV-1. This particular strain was identified in a frozen sample taken from a captive member of the sub-group of chimpanzees known as Pan troglodytes troglodytes (P. t. troglodytes), which were once common in west-central Africa.
The researchers (led by Paul Sharp of Nottingham University and Beatrice Hahn of the University of Alabama) made the discovery during the course of a 10-year long study into the origins of the virus. They claimed that this sample proved that chimpanzees were the source of HIV-1, and that the virus had at some point crossed species from chimps to humans.
Their final findings were published two years later in Nature magazine³ . In this article, they concluded that wild chimps had been infected simultaneously with two different simian immunodeficiency viruses which had "viral sex" to form a third virus that could be passed on to other chimps and, more significantly, was capable of infecting humans and causing AIDS.
These two different viruses were traced back to a SIV that infected red-capped mangabeys and one found in greater spot-nosed monkeys. They believe that the hybridisation took place inside chimps that had become infected with both strains of SIV after they hunted and killed the two smaller species of monkey.
They also concluded that all three 'groups' of HIV-1 - namely Group M, N and O (see our strains and subtypes page for more information on these) - came from the SIV found in P. t. troglodytes, and that each group represented a separate crossover 'event' from chimps to humans.

How could HIV have crossed species?

It has been known for a long time that certain viruses can pass between species. Indeed, the very fact that chimpanzees obtained SIV from two other species of primate shows just how easily this crossover can occur. As animals ourselves, we are just as susceptible. When a viral transfer between animals and humans takes place, it is known as zoonosis.
Below are some of the most common theories about how this 'zoonosis' took place, and how SIV became HIV in humans:

The 'hunter' theory

The most commonly accepted theory is that of the 'hunter'. In this scenario, SIVcpz was transferred to humans as a result of chimps being killed and eaten or their blood getting into cuts or wounds on the hunter. Normally the hunter's body would have fought off SIV, but on a few occasions it adapted itself within its new human host and became HIV-1. The fact that there were several different early strains of HIV, each with a slightly different genetic make-up (the most common of which was HIV-1 group M), would support this theory: every time it passed from a chimpanzee to a man, it would have developed in a slightly different way within his body, and thus produced a slightly different strain.

“Retroviral transfer from primates to hunters is still occurring even today”

An article published in The Lancet in 2004⁴ , also shows how retroviral transfer from primates to hunters is still occurring even today. In a sample of 1099 individuals in Cameroon , they discovered ten (1%) were infected with SFV (Simian Foamy Virus), an illness which, like SIV, was previously thought only to infect primates. All these infections were believed to have been acquired through the butchering and consumption of monkey and ape meat. Discoveries such as this have led to calls for an outright ban on bushmeat hunting to prevent simian viruses being passed to humans.  

back to topWhen?

During the last few years it has become possible not only to determine whether HIV is present in a blood or plasma sample, but also to determine the particular subtype of the virus. Studying the subtype of virus of some of the earliest known instances of HIV infection can help to provide clues about the time it first appeared in humans and its subsequent evolution.
Four of the earliest known instances of HIV infection are as follows:

1. A plasma sample taken in 1959 from an adult male living in what is now the Democratic Republic of the Congo.¹¹
2. A lymph node sample taken in 1960 from an adult female, also from the Democratic Republic of the Congo.¹²
3. HIV found in tissue samples from an American teenager who died in St. Louis in 1969.¹³
4. HIV found in tissue samples from a Norwegian sailor who died around 1976.¹⁴

A 1998 analysis of the plasma sample from 1959 suggested that HIV-1 was introduced into humans around the 1940s or the early 1950s.¹⁵
In January 2000, the results of a new study¹⁶ suggested that the first case of HIV-1 infection occurred around 1931 in West Africa. This estimate (which had a 15 year margin of error) was based on a complex computer model of HIV's evolution.
However, a study in 2008¹⁷ dated the origin of HIV to between 1884 and 1924, much earlier than previous estimates. The researchers compared the viral sequence from 1959 (the oldest known HIV-1 specimen) to the newly discovered sequence from 1960. They found a significant genetic difference between them, demonstrating diversification of HIV-1 occurred long before the AIDS pandemic was recognised.
The authors suggest a long history of the virus in Africa and call Kinshasa the “epicentre of the HIV/AIDS pandemic” in West Africa. They propose the early spread of HIV was concurrent with the development of colonial cities, in which crowding of people increased opportunities for HIV transmission. If accurate, these findings imply that HIV existed before many scenarios (such as the OPV and conspiracy theories) suggest.

What about HIV-2? When did that get passed to humans?

Until recently, the origins of the HIV-2 virus had remained relatively unexplored. HIV-2 is thought to come from the SIV in Sooty Mangabeys rather than chimpanzees, but the crossover to humans is believed to have happened in a similar way (i.e. through the butchering and consumption of monkey meat). It is far rarer, significantly less infectious and progresses more slowly to AIDS than HIV-1. As a result, it infects far fewer people, and is mainly confined to a few countries in West Africa.
In May 2003, a group of Belgian researchers published a report¹⁸ in Proceedings of the National Academy of Science. By analysing samples of the two different subtypes of HIV-2 (A and B) taken from infected individuals and SIV samples taken from sooty mangabeys, Dr Vandamme concluded that subtype A had passed into humans around 1940 and subtype B in 1945 (plus or minus 16 years or so). Her team of researchers also discovered that the virus had originated in Guinea-Bissau and that its spread was most likely precipitated by the independence war that took place in the country between 1963 and 1974 (Guinea-Bissau is a former Portuguese colony). Her theory was backed up by the fact that the first European cases of HIV-2 were discovered among Portuguese veterans of the war, many of whom had received blood transfusions or unsterile injections following injury, or had possibly had relationships with local women.

back to topWhere?

The question of exactly where the transfer of HIV to humans took place, and where the 'epidemic' officially first developed has always been controversial. Some have suggested that it is dangerous to even try to find out, as AIDS has frequently been blamed on an innocent person or group of individuals in the past. However, scientists remain keen to find the true origin of HIV, as most agree it is important to understand the virus and its epidemiology in order to fight it.

So did it definitely come from Africa?

Given the evidence we have already looked at, it seems highly likely that Africa was indeed the continent where the transfer of HIV to humans first occurred (monkeys from Asia and South America have never been found to have SIVs that could cause HIV in humans). In May 2006, the same group of researchers who first identified the Pan troglodytes troglodytes strain of SIVcpz, announced that they had narrowed down the location of this particular strain to wild chimpanzees found in the forests of Southern Cameroon¹⁹ . By analysing 599 samples of chimp droppings (P. T. troglodytes are a highly endangered and thus protected species that cannot be killed or captured for testing), the researchers were able to obtain 34 specimens that reacted to a standard HIV DNA test, 12 of which gave results that were virtually indistinguishable from the reactions created by human HIV. The researchers therefore concluded that the chimpanzees found in this area were highly likely the origin of both the pandemic Group M of HIV-1 and of the far rarer Group N. The exact origins of Group O however remain unknown.
HIV Group N principally affects people living in South-central Cameroon, so it is not difficult to see how this outbreak started. Group M, the group that has caused the worldwide pandemic, was however first identified in Kinshasa, in the Democratic Republic of Congo. It is not entirely clear how it transferred from Cameroon to Kinshasa, but the most likely explanation is that an infected individual travelled south down the Sangha river that runs through Southern Cameroon to the River Congo and then on to Kinshasa, where the Group M epidemic probably began.
Just as we do not know exactly who spread the virus from Cameroon to Kinshasa, how the virus spread from Africa to America is also not entirely clear. However, recent evidence suggests that the virus may have arrived via the Caribbean island of Haiti.

Why is Haiti significant?

The AIDS epidemic in Haiti first came to light in the early 1980s, at around the same time that cases in the USA were being uncovered. Following the discovery of a number of Haitians with Kaposi's Sarcoma and other AIDS-related conditions, medical journals and books began to claim that AIDS had come from Haiti, and that Haitians were responsible for the AIDS epidemic in the United States.
These claims, which were often founded on dubious evidence, fuelled pre-existing racism in the US and many Haitians suffered severe discrimination and stigma as a result. A large number of Haitian immigrants living in the US lost their jobs and were evicted from their homes as Haitians were added to homosexuals, haemophiliacs and heroin users to make the 'Four-H Club' of groups at high risk of AIDS.²⁰
The emotionally-charged culture of blame and prejudice that surrounded HIV and AIDS in the early years meant that it soon became politically difficult to present epidemiological findings in a neutral and objective way. For many years the link between Haiti and the US epidemic was therefore dropped as a subject.