Free Spillover: Animal Infections and the Next Human Pandemic by David Quammen Page A

carefully packaged syringes and needles and vials and instruments, medical gloves, hazmat suits, tents and tarps, rice, fufu, canned tuna, canned peas, several boxes of bad red wine, numerous bottles of water, a couple of folding tables, and seven stackable white plastic chairs. With these tools and luxurious provisions we established a field camp across the river from Moba. Our team included an expert tracker named Prosper Balo, plus other wildlife veterinarians, other forest guides, and a cook. Prosper had worked at Lossi before and during the outbreak. With his guidance, we would prowl the complex of bais, all full of succulent vegetation and previously famed for the dozens of gorillas that came there daily to eat and relax.
    Billy Karesh had visited the same area twice previously, before Ebola struck, seeking baseline data on gorilla health. During a 1999 trip, he had seen sixty-two gorillas here in one day. In 2000 he returned to try darting a few. “Every day,” he told me, “every bai had at least a family group.” Not wanting to be too disruptive, he had tranquilized only four animals, weighed them and examined them for obvious diseases (such as yaws, a bacterial skin infection), and taken blood samples. All four apes had tested negative for Ebola antibodies. This time things were different. He wanted blood serum from survivors of the 2002 die-off. So we began, with high expectations. Days passed. As far as we could see, there were no survivors.
    Precious few, anyway—not enough to make gorilla-darting (which is always a parlous enterprise, with some risk for both the darter and the dartees) productive of data. Our stakeout at Moba lasted more than a week. Early each morning we crossed the river, walked quietly to one bai or another, concealed ourselves in thick vegetation along the edge, and waited patiently for gorillas to appear. None did. Often we hunkered in the rain. When it was sunny, I read a thick book or dozed on the ground. Karesh stood ready with his air rifle, the darts loaded full of tilletamine and zolazepam, drugs of choice for tranquilizing a gorilla. Or else we hiked through the forest, following closely behind Prosper Balo as he searched for gorilla sign and found none.
    On the morning of day 2, along a swampy trail to the bais, we saw leopard tracks, elephant tracks, buffalo tracks, and chimpanzee sign, but no evidence of gorillas. On day 3, with still no gorillas, Karesh said: “I think they’re dead. Ebola went through here.” He figured that only a lucky few, uninfected by the disease or else resistant enough to survive it, remained. Then again, he said, “those are the ones we’re interested in,” because they, if any, might carry antibodies. On day 4, separating from the rest of us, Karesh and Balo managed to locate a single, distraught male gorilla from the sound of his chest beats and screaming barks, and to crawl within ten yards of him in the thick underbrush. Suddenly the animal stood, only his head visible, in front of them. “I could have killed him,” Karesh said later. “Pitted him.” Drilled him between the eyes, that is, but not immobilized him with a safe shot to the flank. So Karesh held his fire. The gorilla let out another bark and ran off.
    My notes from day 6 include the entry: “Nada nada nary gorilla nada.” On our final chance, day 7, Balo and Karesh tracked another couple of animals for hours through the boggy forest without getting so much as a good glimpse. Gorillas had become desperately scarce, round about Moba Bai, and the stragglers were fearfully shy. Meanwhile the rain continued, the tents grew muddy, and the river rose.
    When we weren’t in the forest, I spent time in camp talking with Karesh and the three Africa-based WCS veterinarians on his team. One was Alain Ondzie, a lanky and bashful Congolese, trained in Cuba, fluent in Spanish as well as French and several Central African languages, with a likable tendency to dip his head and giggle