Opinion | The Virus and Bats

Some people also blame bats for the dangerous pathogens they carry — including, potentially, the precursor of the new coronavirus, SARS-CoV-2. That virus may have gotten into us from one of the several kinds of horseshoe bat from southern China. If so, the fateful event probably had more to do with what some human wanted from bats than with what some bat wanted from humans.

Bat viruses spill into humans; they don’t climb into us. They don’t seek us out. And the spilling generally happens when we intrude upon bats in their habitats, excavating their guano for fertilizer, capturing them, killing them or transporting them live to markets, or otherwise initiating a disruptive interaction.

Scientists haven’t yet discovered (and they may never) just which such encounter brought this coronavirus to humanity. But you can be confident that it didn’t happen because some Chinese rufous horseshoe bat flew into Wuhan and bit a poor man on the toe.

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The most lethal of bat-borne viruses, for humans, is rabies, now recognized as one member of a diverse group called the lyssaviruses (as in Lyssa, the Greek goddess of frenzy and rage), most of them associated with bats. Humans have been aware of rabies at least since Democritus, in the fifth century B.C. We’ve seen it in our dogs, sometimes driven mad, like Old Yeller, and occasionally in an unlucky person who got bit. The fatality rate for rabies, absent prompt post-exposure vaccination, is nearly 100 percent, and the disease still kills tens of thousands of people each year.

But from what original source did rabies get into dogs or raccoons or skunks or the other carnivores from whose saliva it drips into a bite wound? The first clue to that mystery came in 1911, when rabies virus was reported among bats by an Italian scientist in Brazil, Antonio Carini, who noted the odd detail that it didn’t seem to make the bats sick. That suggested a long relationship between the bats and the virus, which had perhaps reached a mutual accommodation: a secure habitat for the virus, no symptoms for the host.

Although rabies was the topic that dominated research in this field for much of the 20th century, a few other bat-borne viruses turned up, mostly as incidental discoveries by scientists studying something else. Rio Bravo virus, for instance, found among some California bats in 1954 and related to the yellow fever virus, was one. Tacaribe virus, carried by both bats and mosquitoes in Trinidad, was another. These viruses yielded scientific papers but not newspaper headlines, because they weren’t causing human deaths.

Soon, too, there appeared some new killer viruses, though without (at first) any clear linkage to bats. Marburg virus as well as the most lethal and infamous of the Ebolas, now known as Zaire ebolavirus, caused gruesome illness and death with their first recognized outbreaks among humans, during the late 1960s and 1970s. But their confirmed (Marburg) or probable (Zaire ebolavirus) connections to bats as reservoirs were not established by science until later.