The HIV epidemic is a century old.
A widely-praised new study, published in the October 1 edition of Nature, has placed HIV's first jump from chimpanzee to man sometime between 1884 and 1924. This shifts the estimated window of time back nearly three decades from a previous estimate.
Calling the study 'an elegant piece of work,' National Institute for Allergy and Infectious Diseases director Anthony Fauci stressed the importance of confirming that HIV 'was around decades and decades before it became an obvious epidemic.'
Michael Worobey, an evolutionary biologist at the University of Arizona in Tucson, led the research team, which was supported in part by a grant from the NIAID. Through some slick detective work, Worobey uncovered the second oldest specimen of HIV, locked away in a paraffin-preserved lymph node biopsy taken from a woman who died in 1960 in the town known today as Kinshasa, in the Democratic Republic of the Congo.
The previous major study on HIV's genesis, which placed the cross-species leap at about 1930, relied on an HIV specimen taken from the same Congolese town in 1959. With a new sample added to the mix, Worobey's team was able project that it would've taken about 60 years for the two variations of the virus to evolve from a common ancestor.
Rosemary McKaig, an epidemiologist in NIAID's division of AIDS, said that such historical mapping of the HIV genome can help identify which segments of the viral code are more stable over time, which, she said, 'would make excellent targets for drugs or vaccines. Moreover, knowing how the virus has evolved in the past can give scientists insight into the ways in which HIV might develop resistance to currently available medications.'
The study attributes the rise of HIV to the parallel spread of colonial urbanization in central Africa throughout the early 20th century.
'Assuming that that's not a coincidence,' said Worobey, 'it means that it was urbanization and the associated changes in human behavior that allowed the virus to move more smoothly from person to person and actually spread rather than go extinct.'
The research of microbiologist Beatrice H. Hahn, also of the University of Arizona, has identified a small region of southern Cameroon as the likely site where bush meat hunters may have first come into contact with infected chimpanzee blood. She said the earliest HIV-positive humans probably traveled along the waterways that feed directly into Kinshasa, over 400 miles south of the native chimp habitat. By the 1950s, there were a few thousand cases of HIV in this new epicenter of the oncoming global pandemic, Hahn's estimates.
Worobey hopes his research will help re-energize investments in HIV prevention by focusing on how human behavior drives the spread of the virus.
'I think people don't fully appreciate that it's within our power to overcome the epidemic,' he said. 'We can't turn back the clock'and no one would want to turn back the clock and go to a pre-urban environment'but there are lots of things we can to do more efficiently target prevention efforts to high-risk groups. Most of the time, these are exactly the same things you want to be doing to help out people who are infected already.'