LIANE HANSEN, host:
Twenty-five years ago tomorrow, doctors in Los Angeles first reported cases of what turned out to be the global catastrophe we now know as AIDS. Since then, 55 million people have been infected with the AIDS virus, and it kills around 8,000 people a day.
In the days surrounding the anniversary, NPR is broadcasting a number of stories about AIDS and its effect around the world. Today we examine its origins. Scientists, politicians, and conspiracy theorists have debated for years where AIDS began. Recently, researchers found the missing link: the immediate ancestor of the Human Immunodeficiency Virus.
NPR's Richard Knox reports that the discovery clarifies the story of how a chimpanzee virus touched off the deadliest pandemic since the Middle Ages.
RICHARD KNOX reporting:
Scientists have tracked the ancestor of HIV to something like a zip code, a remote corner of the West African rain forest. The virus still circulates in three small communities of chimpanzees like these from a documentary.
(Soundbite of chimpanzees)
KNOX: The chimps who harbor the ancestor virus live in the forests of Southeastern Cameroon, on the edge of the vast Congo River basin. Cameroonian chimps got the virus probably many thousands of years ago by killing and eating monkeys.
Professor JIM MOORE (University of California, San Diego): Chimpanzees eat monkeys quite regularly. They're pretty carnivorous. And so it's not hard to imagine a chimpanzee being bitten while it's attacking another monkey and picking up virus that way.
KNOX: Jim Moore is a primate specialist at the University of California in San Diego. He's been posing questions about where AIDS came from, such as why did this all happen in the late 20th century?
Prof. MOORE: For me, as a comparative primatologist, the more interesting question is why didn't it happen sooner?
KNOX: Sooner, because after all, humans have hunted chimps for eons. There've been lots of chances for (unintelligible) hunters to get infected with the chimp version of HIV through a bite or cut. By why did one particular infection start a pandemic?
Some people blame Africa, or the behavior of Africans, for AIDS. But Moore says that's way too simplistic.
Prof. MOORE: There's something that somehow they did wrong. I think it's important to recognize that that's wrong. Every scenario for the origin of HIV has it taking place during the period of colonial rule in Africa, and taking place as a result of colonial practices.
KNOX: Colonial practices like forced labor and well-intentioned medical campaigns.
Experts think it was around 1930 that HIV got its big chance, give or take a decade. We know that because there viruses mutate at a constant rate. So scientists can clock how long ago HIV diverged from its chimpanzee ancestor.
The date is important because of what was going on in West Africa then. The French and Belgians were hell-bent to extract rubber and ivory.
(Soundbite of Cameroonian workers)
They conscripted workers, like these Cameroonians, recorded in 1954, to build the railways to ship their booty to the coast. Moore says this is how it might have happened.
Prof. MOORE: You have a rubber collecting crew coming into the village. The routine practice was to kill a few people as an example, or take their children hostage and kill them if the rubber didn't come in. So these patrols were avoided. And so you could have someone seeing the boat come upriver, flee into the forest, perhaps not very used to butchering chimpanzees, so he gets cut in the process of feeding himself and family in the forest.
KNOX: And get the virus that would become HIV. Then, he ventures into another village.
Prof. MOORE: He gets caught by a press gang getting workers for the railroad, taken down the hundreds of kilometers, arrives exhausted and hungry, and receives a whole series of injections along with everybody else in his group.
KNOX: With unsterilized syringes.
Prof. MOORE: So you've got a few hundred people injected probably with one or two needles.
KNOX: Syringes were expensive then. Handmade. In one campaign, French doctors used six syringes to inject 80,000 African workers with a medicine for sleeping sickness.
Prof. MOORE: The opportunities for passing blood from one person to another person to another person to another person would be all over the place.
KNOX: The railroad worker, or someone who got HIV from his blood, would be starving and overworked. His immunity would be low. He might visit a camp prostitute. It was a stew of risk factors ideal for spreading a virus.
In Moore's scenario, that first HIV infected man eventually gets sick, and...
Prof. MOORE: Eventually dies of what we would call AIDS, or dies of something else, but having had the virus long enough so that it could adapt and be transmitted to somebody else.
KNOX: And maybe dozens of others.
Now that we know about the origins of HIV in time, what about place? Beatrice Hahn and her colleagues say they've pinned down.
Prof. BEATRICE HAHN (University of Alabama, Birmingham): We were able to hone in, if you will, to zero down on the area in the forest that must have given rise to the virus that is now spreading globally and basically has caused the AIDS pandemic.
KNOX: Knowing place as well as time makes the puzzle pieces fit together. The origins of the AIDS virus lie along the Singa(ph) River and its tributaries. These rivers flow south into the great Congo.
Five hundred miles downstream is a colonial capital Leopoldville, now known as Kinshasa. When HIV arrived in Leopoldville-Kinshasa, it was one of the burgeoning cities of late colonial Africa, rich with a new kind of urban life and music like this, recorded in the mid-50s.
(Soundbite of African music)
KNOX: Kinshasa is where scientists documented the first case of HIV, a Bantu man who participated in a medical study in 1959. His blood lay in a freezer until the 1980s, when the new AIDS blood test showed it contained HIV-1. The virus' closest relative? The one Hahn found circulating today in those Cameroonian chimps.
Prof. HAHN: From there, Southeastern Cameroon, it appears to have somehow made its way to Kinshasa, where the pandemic was likely spawned.
KNOX: Kinshasa grew even faster after independence in 1960. By then, cheap, plastic syringes were in wide use, but they weren't usually sterilized. That spread blood-borne viruses even more efficiently.
Kinshasa was one of the first places doctors recognized AIDS in Africa, three years after they discovered it in American gay men. Many women giving birth at Kinshasa's largest hospital were infected. By then, the virus had spread all the way to Lake Victoria, a thousand miles to the east.
There have been other theories of where HIV started and how it spread. The idea that it was a CIA plot, for instance, or the idea that an American-led polio vaccination campaign unintentionally gave a million Africans a chimp virus in the late 1950s.
Unidentified Announcer: ...return to political quiet after the recent disturbances. Leopoldville engages in an all-out fight against infantile paralysis, crowding every clinic with mothers and their children, the latter to receive orally administered shots of a new vaccine against the scourge of childhood. It is a live virus preparation developed in the United States by...
KNOX: Some think the oral polio vaccine was contaminated by the chimpanzee version of HIV. Allegedly, the vaccine makers grew the polio virus in kidney cells from chimps infected with the virus.
Hahn says her new evidence lays that idea to rest. If the vaccinators did use chimp kidneys to make their polio vaccine in a Congolese lab near what is now called Kisingani, Hahn says would not have been of the subspecies that harbors the pandemic virus ancestor.
Dr. HAHN: Well, you would have to come up with a pretty convincing scenario that would explain how chimpanzees or the viruses from the southeastern corner of Cameroon end up around Kisingani.
KNOX: A river trip of around 800 miles. But there's still one big question. How did a virus that sprang from chimpanzees in Cameroon touch off a new disease first noticed among gay men in Los Angeles and New York City? Clearly, jet travel and rapidly changing sexual behavior enabled the virus to jump to North America via Europe or perhaps Haiti. But exactly how, science has yet to explain and may never be able to.
Richard Knox, NPR News.
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