Right now, at least 10,000 viruses capable of infecting humans are lurking in the wild, most of them circulating undetected in animals. Typically, these diseases don’t end up reaching us. But in some cases, a virus will leap from one species to another, a phenomenon known as a “viral spillover.” When emerging infectious diseases hop between animal hosts, and, eventually, to humans, the consequences can be catastrophic.
Viral spillover is the culprit behind some of the most damaging infections in history: In late 2002, the coronavirus that causes SARS, or severe acute respiratory syndrome, jumped from bats to people through an intermediate host, a weasel-like creature called a civet. A decade later, in 2013, an 18-month-old boy from a village in Guinea was playing near a hollow tree that contained bats carrying a mysterious disease — later identified as Ebola. The child became infected and died, possibly setting off an ...
