By now the story of how new viral threats emerge should be familiar – the close contact with infected animals, the virus leaping between species, the “patient zero” who catches it first, the super-spreaders who carry it across the globe. But what occurs at the end of a virus’s existence is only just starting to gather interest.
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Even with a Herculean effort to eradicate [Ebola] from human populations, it will still remain circulating in its original host – bats. This means the only way to drive the virus to extinction is to eliminate it in the wild, which is a near-impossible task.
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“Sars went away because there’s no other obvious host,” says [microbiologist Stanley] Perlman. Sars is thought to have made the leap to humans via a palm civet… Perlman points out that the virus couldn’t just retreat back to this species, because they aren’t commonly infected.
The same cannot be said for Covid-19, which again, is thought to have originally belonged to bats, before briefly being passed on to another animal – possibly pangolins – and eventually humans. “With Covid-19, the reservoir is now us,” says Perlman. In fact, it’s become so much of a human virus that scientists have begun to wonder if it will spread the other way around – from humans to wildlife, in a kind of “reverse spillover”, if you will. This would make it even harder to stamp out.
