'Molecular Clock' Moves Origin of AIDS Epidemic to 1930

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Feb. 1, 2000 (San Francisco) -- Scientists at the Los Alamos National Laboratory have used a unique computer model to demonstrate that the crucial event or chain of events starting the AIDS epidemic probably occurred early in the 20th century, possibly around 1930. This challenges a new account suggesting that an HIV-contaminated batch of polio vaccine may have been the trigger in the 1950s.

Bette Korber, PhD, presented her data on the origins of HIV to scientists here attending the 7th Conference on Retroviruses and Opportunistic Infections. From ground zero just decades ago, the AIDS epidemic has already killed 16 million people worldwide, and Korber says that determining the chronological start is more than just an academic exercise -- some of the analytical techniques she used might lead to vaccines or better drugs for the disease.

"I'm excited about the application, and I think the tools are fundamental tools to say, look at evolution [of the virus] within an individual, look at evolution in the context of therapy," says Korber. In a very real sense, what Korber did was build family trees of HIV with the help of a supercomputer capable of doing a trillion calculations per second.

Using 160 strains of the virus, Korber created what she calls a "molecular clock" to see how the viral mutations developed over time from a "common ancestor."

The staggering number of combinations sprouted into statistical "trees" with intertwined branches or viral subgroups. All this led her back decades before the epidemic was discovered.

Ultimately, Korber came up to what she describes as an "evolutionary bottleneck" in her model, somewhere between 1910 and 1950, when the infection made a dramatic leap, either from primate to man, or from people at low risk to those at high risk.

"It doesn't necessarily mark the point where a chimp bit a man," Korber says, but it does suggest that the epidemic predates the first known cases in the '70s. And it debunks the theory that contaminated polio vaccine accidentally infected people in Africa during a test in the '50s. The earliest known HIV-infected blood sample was traced to 1959. As many as 1 million people may have been given the suspect vaccine.

Science writer Edward Hooper is advancing the controversial vaccine idea in his recent book The River. Korber, however, considers it unlikely that a diverse virus could have been spawned by this one event, and she has considerable support for that view.

"If [the epidemic's start] had occurred in the '50s, then that would have presupposed the simultaneous introduction of 10 separate sources. ... It's more likely that something happened in the '30s ... and then branched out," Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, tells WebMD. Fauci describes Korber's work as important.

An analysis of a vaccination sample from that '50s experiment is currently underway in an effort to resolve the controversy in time for another scientific meeting in May. Scientists now believe that the HIV epidemic was likely born in Africa, where primates harboring SIVs, viruses similar to HIV, live in close proximity to man.

Beatrice Hahn, MD, of the University of Alabama at Birmingham, writes in the current issue of the journal Science that the most common strain of HIV developed from transmission between a chimp subspeciesand man. Hahn, who has reviewed Korber's work, says that primates have infected man on at least seven occasions with HIV-like viruses.

But why HIV in Africa, and why the early 20th century? Besides a readily available viral pool, Hahn attributes the epidemic, at least in part, to "social disruption, enslavement, urbanization, prostitution, and other socio-behavioral changes not yet fully understood." Another possibility is the extensive use of unsterilized needles.

Hahn tells WebMD that it's critical to follow-up on Korber's studies on the epidemic's origins because there are 24 other primate species that also could harbor deadly but as yet unknown viruses like HIV.

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