Pandemic Spillback: Could Bats Get It from Us?

Thanks to rapid genome sequencing technology and the work of hundreds of dedicated virologists and wildlife biologists around the world, we now have a good idea where SARS-CoV-2, the virus causing the worldwide COVID-19 pandemic, came from. Sometime in the Fall or early Winter of 2019, a closely related bat coronavirus made the leap into a human. It may have gone through an intermediate host first, or maybe not. In either case, it managed to adapt well enough to replicate and spread to another human, a phenomenon called spillover. The rest is history.

While many researchers are working to answer the remaining questions about SARS-CoV-2’s origin story, others are studying an even more pressing issue: what happens next? A recent paper in PLOS Pathogens suggests that the future may hold an ironic twist.

The same promiscuity that allowed this bat virus to make the leap into humans has already been shown to support its movement into domesticated and semi-domesticated animals. This isn’t the first time a coronavirus has demonstrated this ability. One of the established “common cold” coronaviruses, OC43, can hop between humans and cattle.

In principle, we might eventually be able to control the virus even if it gets into our pets and livestock, but what if it also spreads into wild animals? What if we give it back to the bats, for example?

As Olival et al. show, that’s a real possibility. The researchers first looked at historic examples of introduced diseases spreading into and among North American bats, then searched the literature for evidence about coronaviruses in particular. To date, nobody has found any beta-coronaviruses, the viral group that includes SARS-CoV-2, in temperate-zone North American bats. That suggests they would have no prior immunity to this virus.

Mapping the migration routes and looking at habitats and biology of these animals, the authors conclude that many species of North American bats could be exposed to SARS-CoV-2, and would be susceptible to it. Given how poorly the US has managed its response to the pandemic, there’s no shortage of virus circulating among humans on this continent, so it may only be a matter of time before the bats start catching it from us.

While the “spillback” of the pandemic virus into wild bats may not happen anytime soon, it could have far-reaching impacts if it does. For example, many North American bat species, already decimated by white nose syndrome, are teetering on the brink of extinction. They may not be able to tolerate another introduced pathogen, and losing these bats could destabilize entire ecosystems. At the same time, a bat reservoir of SARS-CoV-2 could provide an ongoing source of new spillover events back into humans, complicating control of the virus. To address that, Olival et al. advocate stepping up efforts to track bat diseases.

The paper is a literature review. Other than a detailed visualization of bat migration routes, the authors don’t present any new data. One reason is that studies such as the ones they propose, monitoring infectious agents in wild bats, haven’t been well-funded in the past. Indeed, one of the leading global efforts to look at circulating bat viruses had its funding cut in April for no good reason. Now the bats aren’t the only ones flying blind.

6 replies on “Pandemic Spillback: Could Bats Get It from Us?”

They may not be able to tolerate another introduced pathogen, and losing these bats could detabilize entire ecosystems.

destablize, I would think.

But the bats might also lose their tables. Seriously, though, thanks for the correction. I’ll edit it in.

Great topic, Time is the only dimension this awareness gives us.
Given then current shift in dicotamonys of science/health and economy/environment, may I ask what a individual can do to encourage our representatives in leadership to make the decisions that are in the interests of life that includes us with some capacity to smile retained when you wake up. Thanks from Australia.

I like the “Examples of other “hands-off” [research] methods” section on page 10 of the paper because the focus is on scalable solutions. I enjoy TWiV and especially the episodes with Ralph Baric and Peter Daszak because of the focus on ecology and animal models but I’m frustrated that these topics are not explored in greater depth.

Baric’s peer-reviewed papers and Daszak’s bat anal swab surveys are not timely enough nor do they scale. The questions raised in this paper should have been asked in March and acted on in April. When Baric discusses a potential animal model for SARS-CoV-2 I would appreciate someone on the TWiV panel asking how to scale the number of experiments by 3 or 4 orders of magnitude; if Baric’s lab can’t do it then ask who can.

This paper mentions large scale monitoring via echolocation and I want to know what efforts Daszak has made to engage Amazon, Google, and/or Alibaba to co-develop the required machine learning systems; ironically Amazon sells a product family named Echo that seems well suited to this task. I don’t think North American bat spillover will be important an integrated system to monitor bats and other nocturnal mammals like raccoons should be easy to adapt to South East Asia where it is most needed.

TWiVerse is fun and engaging but I’m disappointed that TWiV doesn’t have a page with a ranked list of unanswered pandemic questions.

Comments are closed.