Origins of HIV/AIDS
It is widely believed that HIV entered the human population as a result zoonosis, the process where a disease jumps the species barrier. In this case SIV, the monkey form of HIV is believed to have jumped the species barrier. The stronger strain of HIV, HIV-1, is almost identical to SIVcpz. SIVcpz is found in a species of chimpanzees known as Pan troglodytes troglodytes which can be found Central-Western Africa. Some researchers claim that this species of chimpanzee was responsible for HIV-1 and at some point SIVcpz jumped the species barrier. However, this theory is often questioned as SIVcpz is a rarer strand that does not often infect chimpanzees.
The other main theory of how SIV jumped the species barrier was published in 2003 by Professor Paul Sharp of Nottingham University and Beatrice Hahn of the University of Alabama. Their research idicated that a red-capped mangabey and a greater spot nosed monkey, both infected with their forms of SIV, had sex and the two strands of the virus combined to create a 3rd type of hybrid virus that was capable of infecting humans within them both. Chimpanzees became infected with this disease when they hunted and killed the smaller monkeys. When humans killed the chimpanzees and ate them, they became infected with the virus.
First Reported Cases
1959: A plasma sample taken from a man in the Democratic Republic of Congo
1969: A tissue sample from a recently deceased American teenager in St. Louis
1976: Tissue samples from a deceased Norwegian sailor.
However, it was not until 1989 that HIV erupted into an epidemic.
Why did it spread?
International Travel: The problem presented by international travel is highlighted in the case study of Patient Zero, or Gaeten Dugas - a flight attendant. Early cases of AIDS have been shown to have direct and indirect links to Gaeten Dugas. It also highlights how the disease could have travelled through a single agent.
Blood Transfusions: In many countries, such as the U.S., blood transfusions were/are paid for. Furthermore, some transfusions require blood from various sources to be pooled together, thus contaminating a larger amount of blood. This blood is also sent worldwide.
Drug Use: HIV can be transmitted through syringes. After the Vietnam War and various Middle East Conflicts, drug use boomed in the 70s and it was possible to borrow, lend or rent equipment.