The next day we continued on through the forest. We were still more than a week from the nearest road. It was excellent gorilla habitat, well structured, rich with their favorite plant foods, and nearly untouched by humans: no trails, no camps, no evidence of hunters. It should have been full of gorillas. And once, in the recent past, it had been: A census of Gabon’s ape populations done two decades earlier, by a pair of scientists from CIRMF, had yielded an estimate of 4,171 gorillas within the Minkébé forest bloc. Nevertheless, during our weeks of bushwhacking, we saw none. There was an odd absence of gorillas and gorilla sign—so odd that, for Fay, it seemed dramatic. This was exactly the sort of pattern, positive or negative, that his methodology was meant to illuminate. During the course of his entire Megatransect he recorded in his notebook every gorilla nest he saw, every mound of gorilla dung, every stem fed upon by gorilla teeth—as well as elephant dung, leopard tracks, and similar traces of other animals. At the end of our Minkébé leg, he subtotaled his data. This took him hours, holed away in his tent, collating the latest harvest of observations on his laptop. Then he emerged.
Over the past fourteen days, Fay informed me, we had stepped across 997 piles of elephant dung and not one dollop from a gorilla. We had passed amid millions of stems of big herbaceous plants, including some kinds (belonging to the family Marantaceae) with nutritious pith that gorillas devour like celery; but not one of those stems, so far as he’d noticed, had shown gorilla tooth marks. We had heard zero gorilla chest-beat displays, seen zero gorilla nests. It was like the curious incident of the dog in the nighttime—a silent pooch, speaking eloquently to Sherlock Holmes with negative evidence that something wasn’t right. Minkébé’s gorillas, once abundant, had disappeared. The inescapable inference was that something had killed them off.
9
The spillover at Mayibout 2 was no isolated event. It was part of a pattern of disease outbreaks across Central Africa—a pattern of which the meaning is still a matter of puzzlement and debate. The disease in question, once known as Ebola hemorrhagic fever, is now simply called Ebola virus disease. The pattern stretches from 1976 (the first recorded emergence of Ebola virus) to the present, and from one side of the continent (Côte d’Ivoire) to the other (Sudan and Uganda). The four major lineages of virus that showed themselves during those emergence events are collectively known as ebolaviruses. On a smaller scale, within Gabon alone, there has been a tight clustering of Ebola incidents: three in less than two years, and all three rather closely localized in space. Mayibout 2 was the middle episode of that cluster.
An earlier outbreak began during December 1994 in the gold-mining camps on the upper Ivindo, the same area from which Mike Fay later recruited his Gabonese crew. These camps lie about twenty-five miles upstream from Mayibout 2. At least thirty-two people got sick, showing the usual range of symptoms (fever, headache, vomiting, diarrhea, and some bleeding) that suggest Ebola virus disease. The source was hard to pinpoint, though one patient told of having killed a chimpanzee that had wandered into his camp and acted strangely. Maybe that animal was infected, inadvertently bringing the contagion to hungry humans. According to another account, the first case was a man who had come across a dead gorilla, took parts of it back to his camp, and shared. He died and so did others who touched the meat. Around the same time came some reports of chimps, as well as gorillas, seen dead in the forest. More generally, the miners (and their families—these camps were essentially villages) by their very presence, their needs for food, shelter, and fuel, had caused disturbance to the forest canopy and the creatures that lived in it.
From the mining camps, those victims in 1994 were transferred downriver (as they would be again from Mayibout 2) to Makokou General Hospital. Then arose a wave of secondary cases, focused around the hospital or in villages nearby. In one of those villages was a nganga, a traditional healer, whose house may have been a point of transmission between a certain mining-camp victim of the outbreak, seeking folk medicine, and an unlucky local person visiting the healer about something less dire than Ebola. Possibly the virus was passed by the healer’s own hands. Anyway, by the time this sequence ended,