Still, there are compelling reasons to try to settle the issue. Kevin De Cock, a leading AIDS epidemiologist at the U.S. Centers for Disease Control and Prevention, who started a large AIDS-research project in Abidjan in 1988 and now works in Kenya, used to question the relevance of origin studies. "Does any of this matter?" De Cock says. "I've changed my mind. You can't have fifty million infected, sixteen million of whom have died, and say it doesn't matter how this came about. Conditions that expose humans to these simian viruses have probably increased. You can't say from a public-health perspective that those are of no importance."
A better understanding of the origin of AIDS could have an impact on efforts to combat other diseases as well. Omu Anzala, an AIDS-vaccine researcher at the University of Nairobi, says that ripples from The River have "caused many problems" in Kenya. "When people read The River and they are not very scientific, the arguments are pretty convincing," he says. Claiming that the vaccine contains HIV, some Kenyan clergymen have recently discouraged their countrymen from taking part in the current campaign to eradicate polio (which uses a thoroughly tested, contaminant-free OPV). "In the last six or seven months we've been trying to vaccinate as many people as we can," Anzala says. "But certain segments of society have been saying, 'Who knows whether the vaccine isn't contaminated?'"
PARTWAY down the packed-mud road that leads from Franceville to Okondja, Telfer stopped his Land Cruiser so that we could speak with two hunters. One man had a shotgun slung over his shoulder; the other had a machete and a tall wooden cane. Both appeared to be at least in their fifties. Through an interpreter who works with Telfer, I asked the men their ages. Neither had any idea. The interpreter asked them a question of his own: "Have you ever heard of World War Two?" Again they both lifted their shoulders and shook their heads no.
Telfer was making the four-hour round-trip drive to Okondja to take a blood sample from a pet monkey he had found on an earlier expedition. Farther along the route he spotted a dead monkey for sale, splayed on top of an upside-down empty fuel can. Telfer does not want to pay for animals and thereby indirectly encourage trade in bush meat, and so, with his interpreter's help, he delicately negotiated with a woman living in a nearby shack. She agreed to let him take samples from the monkey, a member of Cercopithicus cephus—a species in which no one had yet found an SIV. After putting on latex gloves, he plucked some hair from the animal; he would later do a DNA test to determine where the monkey fits on the cephus family tree. Telfer wrapped a strip of rubber around the monkey and hung it from a hand-held scale: 6.6 pounds. He opened the monkey's mouth and clipped off a bloody piece of tongue. He would have liked to open the belly and take the spleen—a likelier place for SIV to hide—but the village men who by then had clustered around were becoming agitated, and the interpreter discreetly herded us back to the car. A half hour or so later we came upon another recently killed cephus in front of a roadside shack. After similar negotiations with this monkey's owner, Telfer took a tissue sample from the animal's rectum—a location where HIV is frequently found in people.
When we got to Okondja and located the pet, a cephus monkey living in a makeshift cage alongside a house, the owner was not at home. We headed to the marketplace for lunch, where I had a stew made of porcupine (which is not a protected species). The locals took obvious delight in watching us eat there, which pleased Telfer: an important part of his job, he says, is building trust. Over lunch we met another man who has a pet monkey, which Telfer hopes to sample in the future.
We headed back to the caged pet cephus. Its owner had returned, and he agreed to let Telfer take a sample. The first step was to anesthetize the animal with a shot of ketamine. Telfer donned a long leather glove, lifted the tin top off the cage, and tried to grab the monkey. The monkey, of course, wanted no part of this, and madly dodged Telfer's every lunge. Tension rose, amplified by the crowd that had gathered. At last Telfer succeeded in anesthetizing the animal. He placed it on the ground, drew blood from the femoral vein, measured its weight and size, and marked it with a tattoo gun.
As we prepared to leave, a neighbor came up to tell us that she, too, had a pet monkey. We walked a few houses over and saw the animal, a baby cephus, but Telfer decided that it was too small to draw blood from, so we headed back to Franceville. Telfer was pleased with the day's tally: tongue from one fresh kill, rectal tissue from another, blood from a pet, and one adult and one baby pet for future testing.
In June, Preston Marx told me that the pet cephus whose blood we had sampled showed evidence of SIV infection. I sent Telfer an e-mail about it; the subject line on his reply read, "interesting? maybe." As often happens in this kind of work, the preliminary data turned out to be as confusing as they are intriguing: the monkey's blood showed SIV antibodies in one test but not in another. However, researchers extracted strands that appear to be pieces of an SIV, and analysis is proceeding.
Further information about the origin of AIDS will soon emerge from the many research efforts under way. Paul Telfer and his colleagues plan to go to the village where Za-Za came from and take blood samples from human beings there. Telfer is also preparing to collect fecal samples from chimps in the wild. Beatrice Hahn has begun to agree with primatologists who question whether chimp subspecies truly exist. She recently analyzed fecal and urine samples from chimps in Uganda and Côte d'Ivoire and blood from Pan paniscus in the Congo. All tested negative for SIVs, which has led her to wonder whether any chimps outside west central Africa are infected. Martine Peeters, a French researcher who has done pioneering work on the chimp isolates from Gabon, has been testing primate meat from a marketplace in Cameroon. Donald Burke has begun working in Cameroon and hopes to start testing primates in the wild there. At the international AIDS conference held last July in Durban, South Africa, Anne-Mieke Vandamme, a Belgian researcher, presented data that support Bette Korber's 1931 date by means of an entirely different methodology. Even more intriguing, Vandamme's work dates the emergence of SIVcpz and HIV-1 from a common ancestor to about 1700. The analysis of the CHAT samples may suggest directions for new investigations. And the Royal Society meeting will undoubtedly fuel new research as well.
But as Telfer so trenchantly observed, standing quietly in the jungle and looking at nothing in particular, 90 percent of the game is waiting and not seeing much—until the day we see something spectacular.