Sunday, April 22, 2012

Primates & HIV

One of the most stunning, controversial, medical and scientific developments of the last several decades has been the discovery and emergence of HIV, or Human Immunodeficiency Virus. In 2010, the World Health Organization (WHO) estimated that the number of people living with HIV globally was 34 million (AIDS epidemic 2010). In the same year, AIDS (the disease caused by chronic infection with HIV) was responsible for approximately 1.8 million deaths. HIV has also been a scary development in the United States, as viral transmission shifts from a focus on homosexual individuals to heterosexuals of all races and ages. Biologists, anthropologists, and other researchers often disagree on the exact point of origin of HIV, and how it emerged in the human species. These academic questions are exacerbated by the media and conspiracy theorists with a number of creative explanations, many of which have now been discredited. In this blog, I will provide an overview of what actually occurred and address two popular but misguided theories. 

Viral Structure of HIV 1

First of all, there are two forms of HIV circulating in the human species, HIV-1 (common) and HIV-2 (only found in West Africa). Based on genetic analysis, these viruses are derived from a class of viruses called SIVs, or Simian Immunodeficiency Virus (simian aka Old World monkeys). Researchers believe that based on significant genetic similarities, SIVsm (from sooty mangabey monkeys) transformed into HIV-2, and SIVcpz (from chimpanzee monkeys) transformed into HIV-1. While the viral origin is no longer in doubt, exactly why the virus jumped and how it manifests itself differently in humans than primates is still under evaluation. Researchers do know that these SIVs often do not cause deadly disease in infected primates.

This entire body of evidence is contrary to some popular, misguided theories that seek to explain HIV and its financial and social devastation on the emerging world. Jakob Segal's (German university biologist) story is well known - that HIV was engineered by the US government in the 1970s and tested on prisoners before it was released. However, this theory was disproved as genetic analysis shows the virus existed as early as 1920. Another infamous theory comes from the development of the polio virus. This theory claims that the polio virus, developed in chimpanzee tissue, was contaminated with some SIV and introduced to the Congo in Africa in the 1950s - once again, the timing is too late as HIV had already made the jump to the human species.

Theories aside, much work is yet to be done to understand the specific moment or moments of transmission to our species. Genetic analysis can only take us so far, and then cultural anthropologists and historians must step in. Human interaction with nature, including bush meat and blood rituals, are perhaps the key to understanding a critical moment in the history of human disease. 

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