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

in late 1994, eight more carcasses turned up over a short period of time, and again other animals went missing. Two of the chimp bodies, only moderately decayed, were cut open and examined by researchers at Taï. One of those proved to be teeming with an Ebola-like agent, though that wasn’t apparent at the time. During the necropsy, a thirty-four-year-old female Swiss graduate student, wearing gloves but no gown, no mask, became infected. Infected how? There wasn’t any obvious moment of fateful exposure, no slip of the scalpel, no needlestick mishap. Probably she got chimp blood onto a broken patch of skin—a small scratch?—or caught a gentle splash of droplets in the face. Eight days later, the woman started shivering.
    She took a dose of malaria medicine. That didn’t help. She was moved to a clinic in Abidjan, Côte d’Ivoire’s capital, and there treated again for malaria. Her fever continued. On day 5 came vomiting and diarrhea, plus a rash that spread over her whole body. On day 7 she was carried aboard an ambulance jet and flown to Switzerland. Now she was wearing a mask, and so were the doctor and the nurse in attendance. But no one knew what ailed her. Dengue fever, hantavirus infection, and typhoid were being considered, and malaria still hadn’t been ruled out. (Ebola wasn’t at the top of the list because it had never been seen in Côte d’Ivoire.) In Switzerland, hospitalized within a double-door isolation room with negative air pressure, she was tested for a whole menu of nasty things, including Lassa fever, Crimean-Congo hemorrhagic fever, chikungunya, yellow fever, Marburg virus disease, and now, yes, Ebola virus disease. The last of those possibilities was investigated using three kinds of assays, each one specific: for Ebola virus, for Sudan virus, for Reston virus. No positive results. The antibodies in those assays didn’t recognize the virus, whatever it was, in her blood.
    The laboratory sleuths persisted, designing a fourth assay that was more generalized—comprehensive for the whole group of ebolaviruses. Applied to her serum, that one glowed, a positive, announcing the presence of antibodies to an ebolavirus of some sort. So the Swiss woman was the world’s first identified victim of what became known as Taï Forest virus. The chimpanzee she had necropsied, its tissues tested later, was the second victim, recognized posthumously.
    Unlike the chimp, she survived. After another week, she left the hospital. She had lost thirteen pounds and her hair later fell out, but otherwise she was okay. Besides being the initial case of Taï Forest virus infection, the Swiss woman holds one other distinction: She is the first person known to have carried an ebolavirus infection off the African continent. There is no reason to assume that she will be the last.
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    E bolavirus spillovers continued throughout the 1990s and into the twenty-first century, sporadic and scattered enough to make field research difficult, frequent enough to keep some scientists focused and some public health officials worried. In 1995, soon after the Côte d’Ivoire episode, it was Ebola virus in Kikwit, about which you’ve read. Six months after that outbreak, as you’ll also recall, the new one began at Mayibout 2. What I haven’t yet mentioned about Mayibout 2 is that, though the village lies in Gabon, the virus was Ebola as known originally from Zaire, which seems to be the most broadly distributed of the group. At the timber camp near Booué, Gabon, it was Ebola virus.
    Also that year, 1996, Reston virus reentered the United States by way of another shipment of Philippine macaques. Sent from the same export house near Manila that had shipped the original sick monkeys to Reston, Virginia, these went to a commercial quarantine facility in Alice, Texas, near Corpus Christi. One animal died and, after it tested positive for Reston virus, forty-nine others housed in the same room were euthanized as a precaution. (Most of