Spillover

by David Quammen

  The chimpanzee’s virus entered his bloodstream. He got a sizable dose. The virus, finding his blood to be not such a different environment from the blood of a chimp, took hold. Okay, I can live here. It did what a retrovirus does: penetrated cells, converted its RNA genome into double-stranded DNA, then penetrated further, into the cells’ nuclei, and inserted itself as DNA in the DNA genome of those host cells. Its primary targets were T cells of the immune system. A certain protein receptor (CD4) on the surface of those cells, in the Cut Hunter, was not very different from the equivalent receptor (another CD4) on the T cells of the butchered chimpanzee. The virus attached, entered the human cells, and made itself at home. Once integrated into the cellular genome, it was there for good. It was part of the program. It could proliferate in two ways: by cell replication (each time an infected T cell copied itself, the retroviral genome was copied also) and by activating its little subgenome to print off new virions, which then escaped from the T cell and floated off to attack other cells. The Cut Hunter was now infected, though apart from a slash on the hand he felt fine.

  Forget about Gaëtan Dugas. This man was Patient Zero.

  Maybe he carried the chimp carcass, or parts of it, back to his village in triumph—as the boys of Mayibout 2 later carried an Ebola-filled chimp carcass back to theirs. Maybe, if he was Baka, he delivered the whole thing to his Bantu overlord. He didn’t want to eat it anyway. If he was Bantu himself, his family and friends feasted. Or maybe the chimp was a windfall from which he could afford to take special profit. If the season had been bounteous, with some duikers or monkeys killed, some forest fruits and tubers to eat, a good crop of manioc, so that his family wasn’t starving, he may have lugged his chimpanzee to a market, like the one in Moloundou, and traded for cash or some valuable item, such as a better machete. In that case, the meat would have been parceled out retail and many people may have eaten bits of it, either roasted or smoked or dried. But because of how the virus generally achieves transmission (blood-to-blood or sexually) and how it doesn’t (through the gastrointestinal tract), quite possibly none of those people received an infectious dose of virus, unless by contact of raw meat with an open cut on the hand or a sore in the mouth. A person might swallow plenty of HIV-1 particles but, if those virions are greeted by stomach acids and not blood, they would likely fail to establish themselves and replicate. Let’s suppose that fifteen different consumers partook of the chimp meat and that they all remained fine. HIV-negative. Lucky folks. Let’s suppose that only the Cut Hunter became infected directly from the chimp.

  Time passed. The virus abided and replicated within him. His infectiousness rose high during the first six months, as virions in multitude bloomed in his blood; then the viremia declined some as his body mounted an early immune response, while it still could, and leveled off, for a period of time. He noticed no effects. He passed the virus to his wife, eventually also to one of the four other women with whom he had sex. He suffered no immune deficiency—not yet. He was a robust, active fellow who continued to hunt in the forest. He fathered a child. He drank palm wine and laughed with his friends. And then a year later, let’s say, he died violently in the course of an elephant hunt, an activity even more perilous than butchering chimpanzees. He was one of seven men, all armed with spears, and the wounded elephant chose him. He took a tusk through the stomach, momentarily pinning him to the ground. You could see the tusk hole in the dirt afterwards, as though a bloody stake had been driven in and pulled. Of the men who scooped him up, the women who prepared him for burial, none had an open cut and so they were spared infection. His son was born HIV-negative.

  The Cut Hunter’s widow found a new man. That man was circumcised, free of genital sores, and lucky; he didn’t become infected. The other woman who had been infected by the Cut Hunter took several partners. She infected one. This fellow was a local chief, with two wives and occasional access to young village daughters; he infected both wives and one of the girls. The chief’s wives remained faithful to him (by constraint of circumstance if not by choice), infecting no one. The infected girl eventually had her own husband. And so, onward. You get the idea. Although sexual transmission of the virus occurred less efficiently from female to male, and not all so efficiently from male to female, it was just efficient enough. After several years, a handful of people had acquired the virus. And then still more, in time, but not many. Social life was constrained by small population size, absence of opportunity, and to some degree mores. The virus survived with an R0 barely above 1.0. It passed to a second village, in the course of neighborly interactions, and then a third, but it didn’t proliferate quickly in any of them. No one detected a wave of inexplicable deaths. It smoldered as an endemic infection at low prevalence in the populace of that little wedge of terrain, between the Ngoko River and the upper Sangha, where life tended to be short and hard. People died young from all manner of mishaps and afflictions. If a young man, HIV-positive, was killed in a fight, no one knew anything about his blood status except that it had been spilled. If a young woman, HIV-positive, died of smallpox during a local outbreak, likewise she left no unusual story.

  In some cases, during those early years, an infected person may have lived long enough to suffer immune failure. Then there were plenty of ready bugs, in the forest, in the village, to kill him or her. That wouldn’t have seemed remarkable either. People died of malaria. People died of tuberculosis. People died of pneumonia. People died of nameless fever. It was routine. Some of those people might have recovered, had their immune systems been capable, but no one noticed a new disease. Or if someone did notice, the report hasn’t survived. This thing remained invisible.

  Meanwhile the virus itself may have adapted, at least slightly, to its new host. It mutated often. Natural selection was at work. Given a marginal increase in its capacity to replicate within human cells, leading to increased levels of viremia, its efficiency of transmission may have increased too. By now it was what we would call HIV-1 group M. A human-infecting pathogen, rare, peculiar, confined to southeastern Cameroon. Maybe a decade went by. The bug survived. Spillovers of SIVcpz into humans had almost certainly occurred in the past (plenty of chimps were butchered, plenty of hunters were cut) and resulted in previous chains of infection, but those chains had been localized and short. The smoldering outbreak had always come to a cold end. This time it didn’t. Before such burnout could occur, another person entered the situation—also hypothetical but fitted to the facts—whom I’ll call the Voyager.

  The Voyager wasn’t a hunter. Not an expert and dedicated one, anyway. He had other skills. By my imagining, he was a fisherman. He lived not in a forest clearing like the one at Mambele but in a fishing village along the Ngoko River. I picture him as a river boy from childhood; he knew the water; he knew boats. He owned a canoe, a good one, sturdy and long, made from a mahogany log with his own hands, and he spent his days in it. He was a young man with no wife, no children, and just a bit of an appetite for adventure. He had fallen away from his natal community at an early age, becoming a loner, because his father died and the village came to despise his mother, suspecting her of sorcery based on a piece of bad luck and a grudge. He took this as a deep personal bruise; he despised the villagers in return, screw them, and went his own way. It suited him to be alone. He was not an observant Bakwele. He never got circumcised.

  The Voyager ate fish. He ate little else, in fact, besides fish and bananas—and sometimes manioc, which he didn’t plant or process himself but which was easily acquired in trade for fish. He liked the taste and he loved the idea of fish, and there was always enough. He knew where to find fish, how to catch them, their varied types and names. He drank the river. That was enough. He didn’t make palm wine or buy it. He was self-sufficient and contained within his small world.

  He provided fish to his mother and her two younger children, as I see him, a loyal son though an alienated neighbor. His mother still lived at the fringe of the old village. His surplus catch he dried on racks
, or in wet season smoked over a fire, at his solitary riverbank camp. Occasionally he made considerable journeys, paddling miles upstream or drifting downstream, to sell a boatload of fish in one of the market villages. In this way, he had tasted the empowerment of dealing for cash. Brass rods were the prevailing currency, or cowrie shells, and sometimes he may even have seen deutschmarks. He bought some steel hooks and one spool of manufactured line, which had come all the way from Marseille. The line was disappointing. The hooks were excellent. Once he had floated downstream as far as the confluence with the Sangha, a much larger river, powerful, twice as wide as the Ngoko, and had ridden its current for a day—a heady and fearful experience. On the right bank he had seen a town, which he knew to be Ouesso, vast and notorious; he gave it a wide berth, holding himself at midriver until he was past. At day’s end he stopped and slept on the bank; the next day he reversed, having tested himself enough. It took him four days of anxious effort to paddle back up, hugging the bank (except again at Ouesso), climbing through eddies, but the Voyager made it, relieved when he regained his own world, the little Ngoko River, and swollen with new confidence by the time he beached at his camp. This might have occurred, let’s say, in the long dry season of 1916.

  On another occasion, he paddled upstream as far as Ngbala, a river town some miles above Moloundou. It was during his return from that journey, as I posit, that he stopped at Moloundou and there, in his boat, where it was tied for the night in a shaded cove just below town, had sex with a woman.

  She wasn’t his first but she was different from village girls. She was a river trader herself, a Buy ’em–Sell ’em, several years older than he was and considerably more experienced. She traveled up and down the Ngoko and the Sangha, making a living with her wits and her wares and sometimes her body. The Voyager didn’t know her name. Never heard it. She was outgoing and flirtatious, almost pretty. He didn’t think much about pretty. She wore a print dress of bright calico, manufactured, not local raffia. She must have liked him, or at least liked his performance, because she returned to his boat in the shadows the next night and they coupled again, three times. She seemed healthy; she laughed merrily and she was strong. He considered himself lucky that night—lucky to have met her, to have impressed her, to have gotten at no cost what other men paid for. But he wasn’t lucky. He had a small open wound on his penis, barely more than a scratch, where he’d been caught by a thorny vine while stepping ashore from a river bath. No one can know, not even in this imagined scenario, whether the lack of circumcision was crucial to his susceptibility, or the little thorn wound, or neither. He gave the woman some smoked fish. She gave him the virus.

  It was no act of malice or irresponsibility on her part. Despite swollen and aching armpits, she had no idea she was carrying it herself.

  100

  River travel through tropical jungle is uncommonly soothing and hypnotic. You watch the walls of greenery slide by and, unless the channel is narrow enough for tsetse flies to notice your passing and come out from the shores, you suffer almost none of the discomforts. Because the riverbanks represent forest edges, admitting the full blast of sunlight, as closed canopy does not, the vegetation is especially tangled and rife: trees draped with vines, understory impenetrable, thick as an old velvet curtain at the Shubert Theater. It presents an illusion that the forest itself, its interior, might be as dense as a sponge. But to a river traveler that density is immaterial because you have your own open route down the middle. If you’ve walked the forest, which is difficult though not sponge-thick, river journeying is an escape from impediments that feels almost akin to flight.

  For a while after leaving Kika, we favored the Congo side, riding a strong channel. Sylvain knew his preferred line. His assistant, a Baka man named Jolo, handled the outboard while Sylvain supervised, signaling directions from the bow. The pirogue was large and steady enough that Max and I could sit on the gunnels. Immediately we passed a small police post on the right bank, a Congolese counterpart to the Cameroonian one at Kika, and fortunately no one flagged us to stop. Every such checkpoint in Congo is an occasion for passport-stamping and minor shakedowns, and you want to avoid them when you can. Then we puttered past a few villages, widely spaced, each just a cluster of wattle-and-daub houses sited on a high bank to escape inundation in wet season. The houses were topped with thatch and surrounded by banana trees, an oil palm or two, children in rag dresses and shorts. The kids stood transfixed as we passed. How many hours to our destination? I asked Sylvain. Depends, he said. Ordinarily he would stop in villages along the way for trading or passengers, delaying long enough to enter Ouesso by darkness so as to escape notice by the immigration police. Not long after that explanation he did stop, guiding us ashore at a village on the Congo bank, to which he delivered a large plastic tarp and from which, on departure, we gained a passenger.

  It was my charter but I didn’t mind. She was a young woman carrying two bags, an umbrella, a purse, and a pot of lunch. She wore an orange-and-green dress and a bandana kerchief. I might have guessed if I hadn’t been told: She was a Buy ’em–Sell ’em. Her name was Vivian. She lived down in Ouesso and would be glad for the ride home. She was lively and plump, confident enough to be traveling the river alone, trading in rice, pasta, cooking oil, and other staples. Sylvain liked to give her a lift because she was his sister—a statement of status that could be taken literally or not. She might have been his girlfriend or his cousin. Beyond this, I didn’t learn much from Vivian except that her niche still exists, the Buy ’em–Sell ’em role, offering independent-spirited women a form of autonomy not easily found within village life, or even town life, and that the river still functions as a conduit of economic and social fluidity. Mostly she seemed a charming throwback and, though this might be unfair to her, put me in mind of women that the Voyager might have met almost a century earlier. She was a potential intermediary.

  When the rain returned, Max and I and Sylvain and Vivian hunkered beneath our tarp, heads down but peeking out, while Jolo the Baka stolidly motored us on. We passed a solitary fisherman in his canoe, pulling a net. We passed another village from which children stared. Then the rain died again and the storm breeze fell off; the gentle chop disappeared, leaving the river as flat and brown as a cooled café au lait. Mangroves reached out from the banks like groping octopuses. I noticed a few egrets but no kingfishers. In midafternoon we approached the confluence with the Sangha. Along the left bank, the land fell gradually lower and then tapered, sinking away into the water. The Sangha River gripped us, swung us around, and I turned to watch that southeastern wedge of Cameroon recede to a vanishing point.

  The air warmed slightly with an upstream breeze. We passed a large, wooded island. We passed a man standing upright in his dugout, paddling carefully. And then in the distance ahead, through haze, I saw white buildings. White buildings meant bricks and whitewash and governmental presence in something larger than a village: Ouesso.

  Within half an hour we landed at the Ouesso waterfront, with its concrete ramp and wall, where an officer from the immigration police and a gaggle of tip-hungry, scuttering porters awaited. Stepping ashore, we had reentered the Republic of the Congo. We completed the immigration formalities in French and then Max dealt with the bag-grabbing porters in Lingala. Sylvain and Jolo and Vivian melted away. Max was a shier, less forceful fellow than Neville but conscientious and earnest, and now it was his turn to be my fixer. He made some inquiries here along the waterfront and soon had good news: that the big boat, the cargo-and-passenger barge known as le bateau, would be departing tomorrow for Brazzaville, many miles and days further downriver. I wanted us to be on it.

  We found a hotel, Max and I, and in the morning walked to the Ouesso market, which was centered in a squat, pagoda-shaped building of red brick just blocks from the river. The pagoda was big and stylish and old, with a concrete floor and a circular hall beneath three tiers of corrugated metal roof, dating back at least to colonial times. The market had far outgrown it, s
prawling into a warren of wood-frame stalls and counters with narrow lanes between, covering much of a city block. Business was brisk.

  A study of bushmeat traffic in and around Ouesso, done in the mid-1990s by two expat researchers and a Congolese assistant, had found about 12,600 pounds of wild harvest passing through this market each week. That total included only mammals, not fish or crocodiles. Duikers accounted for much of it and primates were second, though most of the primate meat was monkey, not ape. Eighteen gorillas and four chimps were butchered and sold during the four-month study. The carcasses arrived by truck and by dugout canoe. As the biggest town in northern Congo, with no beef cattle to be seen, Ouesso was draining large critters out of the forest for many miles around.

  Max and I snooped up and down the market aisles, stepping around mud holes, dodging low metal roofs, browsing as we had done in Moloundou. Because this was Ouesso, the merchandise was far more abundant and diverse: bolts of colorful cloth, athletic bags, linens, kerosene lanterns, African Barbie dolls, hair falls, DVDs, flashlights, umbrellas, thermoses, peanut butter in bulk, powdered fufu in piles, mushrooms in buckets, dried shrimp, wild fruits from the forest, freshly fried beignets, blocks of bouillon, salt by the scoop, blocks of soap, medicines, bins of beans, pineapples and safety pins and potatoes. On one counter a woman hacked at live catfish with a machete. Just across from her, another woman offered a selection of dead monkeys. The monkey seller was a large middle-aged lady, her hair in cornrows, wearing a brown butcher’s apron over her paisley dress. Genial and direct, she slapped a smoked monkey down proudly in front of me and named her price. Its face was tiny and contorted, its eyes closed, its lips dried back to reveal a deathly smile of teeth. Split up the belly and splayed flat, it was roughly the size and shape of a hubcap. Six mille francs, she said. Beside the first monkey she tossed down another, in case I was particular. Six mille for that one too. She was talking in CFA, the weak Central African currency. Her six thousand francs amounted to US $13, and was negotiable, but I passed. She also had a smoked porcupine, five duikers, and another simian, this one so freshly killed that its fur was still glossy and I could recognize it as a greater spot-nosed monkey. That’s a premium item, Max said, it’ll go fast. Nearby, gobbets of smoked pork from a red river hog were priced at three thousand francs per kilo. All these animals could be hunted legally (though not with snares) and traded openly in Congo. There was no sign of apes. If you want chimpanzee or gorilla meat in Ouesso it can still be had, no doubt, but you’ve got to make private arrangements.