There’s no doubt you’ve heard of HIV, or Human Immunodeficiency Virus. The HIV virus, if left untreated can lead to AIDS, or Acquired Immunodeficiency Syndrome, which leads to progressive immune system failure (http://en.wikipedia.org/wiki/HIV#Discovery). HIV didn’t become a problem in the United States until the 1980s, but was around long before then. Alfred Roca, an assistant Professor at the University of Illinois believes HIV was around for much longer than we believe.
HIV was thought to be originated from SIV, or Simian Immunodeficiency Virus, that infected Chimpanzees in Central Africa. About ninety percent of humans infected with HIV are infected with a strain called HIV-1 Type M, which was believed to have crossed the species barrier anywhere between 1884 and 1924. However, believes that HIV crossed the species barrier many times before 1884, but was most prevalent in rural areas, so it remained undetected.
Why it was a mystery
If HIV was around long before we initially thought, why did it remain undetected. According to Roca, “the persistence of HIV in humans requires population densities typically of larger cities that appeared in West Central Africa during the colonial period.” HIV didn’t spread amongst humans pre-1884 because the population was not dense enough. In addition, diseases spread much faster. Many people would have died early from diseases such as smallpox, and those with compromised immune systems would have been hit first, thus the disease couldn’t spread.
Roca also believes that different strains of HIV could affect people with different genes. Using data from The Human Genome Project, Roca was able to analyze the DNA of the Biaka people, who live in the forests where the chimpanzees responsible for our current HIV pandemic reside and 4 other African populations which live outside the chimpanzees’ range. Research done in the 1980s concluded there are 26 genomic locations that help resist HIV.
The results of the research were astounding. Roca and his team identified four genes that code for proteins that affect the ability of the HIV to affect the host or the progression of the disease. Several of these genes were common among the Biaka people. Though the results aren’t definitive, they show that natural selection does play a part in the transfer of HIV to human populations, which is why the disease didn’t thrive earlier.