procedures (such as barrier nursing by way of isolation wards, latex gloves, gowns, masks, and disposable needles and syringes) usually stop them. Sometimes simpler methods can bring a local spillover to a dead end too. This has probably happened more times than we’ll ever know. Advisory: If your husband catches an ebolavirus, give him food and water and love and maybe prayers but keep your distance, wait patiently, hope for the best—and, if he dies, don’t clean out his bowels by hand. Better to step back, blow a kiss, and burn the hut.
This business about dead-end hosts is the conventional wisdom. It applies to the ordinary course of events. But there’s another perspective to consider. Zoonoses by definition involve events beyond the ordinary, and the scope of their consequences can be extraordinary too. Every spillover is like a sweepstakes ticket, bought by the pathogen, for the prize of a new and more grandiose existence. It’s a long-shot chance to transcend the dead end. To go where it hasn’t gone and be what it hasn’t been. Sometimes the bettor wins big. Think of HIV.
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In late 2007 a fifth ebolavirus emerged, this time in western Uganda.
On November 5, 2007, the Ugandan Ministry of Health received a report of twenty mysterious deaths in Bundibugyo, a remote district along the mountainous border with the Democratic Republic of the Congo (the new name, as of 1997, for what had been Zaire). An acute infection of some unknown sort had killed those twenty people, abruptly, and put others at risk. Was it a rickettsial bacterium, such as the one that causes typhus? An ebolavirus was another possibility, but considered less likely at first, because few of the patients hemorrhaged. Blood samples were gathered quickly, flown to the CDC in Atlanta, and tested there, using both a generalized assay that might detect any form of ebolavirus and specific assays for each of the known four. Although the specific tests were all negative, the general test rang up some positives. So on November 28, the CDC informed Ugandan officials: It’s an ebolavirus, all right, but not one we’ve ever seen.
Further laboratory work established that this new virus was at least 32 percent different genetically from any of the other four. It became Bundibugyo virus. Soon a CDC field team arrived in Uganda to help respond to the outbreak. As usual in such situations, their efforts along with those of the national health authorities involved three tasks: caring for patients, trying to prevent further spread, and investigating the nature of the disease. The eventual tally was 116 people infected, of whom 39 died.
Also as usual, the scientific team later published a journal article, in this case announcing the discovery of a new ebolavirus. First author on the paper was Jonathan S. Towner, a molecular virologist at the CDC with field experience in the search for reservoirs. Besides guiding the lab work, he went to Uganda and did a stint with the response team. The Towner paper contained a very interesting statement, as an aside, concerning the five ebolaviruses: “Viruses of each species have genomes that are at least 30–40% divergent from one another, a level of diversity that presumably reflects differences in the ecologic niche they occupy and in their evolutionary history.” Towner and company suggested that some of the crucial differences between one ebolavirus and another—including the differences in lethality—might be related to where and how they live, where and how they have lived, within their reservoir hosts.
The events in Bundibugyo left many Ugandans uneasy. And they were entitled to their uneasiness: Uganda now held a sorry distinction as the only country on Earth that had suffered outbreaks of two different ebolaviruses (Sudan virus at Gulu in 2000, Bundibugyo virus in 2007), as well as outbreaks of both Ebola virus disease and Marburg virus disease, caused by another filovirus, within a single year. (The creepy circumstances of the Marburg spillover, at a gold mine called Kitaka in June 2007, are part of a story I’ll come to in its turn.) Given such national ill fortune, it’s not surprising that there were rumors, stories, and anxieties circulating among Ugandans, in late 2007, that made tracing genuine ebolavirus leads all the more difficult.
A pregnant woman, showing signs of hemorrhagic fever, delivered her baby and then died. The baby, left in the care of a grandmother, soon died too. That was sad but not peculiar; orphaned infants often die in the hard conditions of a village. More notable was that the