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Why Do Bats Carry So Many Viruses?

Professor of Financial Economics and Part-time Value Investor, Transfin.
Apr 20, 2020 3:28 PM 2 min read

It is likely that the coronavirus presently causing havoc around the world originated in a bat before jumping the species barrier to human beings (experts say this happened through a pangolin in a Wuhan wet market in China). But bats have a notorious history and one wonders why bats carry so many viruses...


One World, Brought Down by Bats

Bats are notoriously virus-prone. They most probably caused the SARS outbreak (through civets) in 2002. MERS, another coronavirus, is suspected to have begun in bats before reaching camels and then humans. Bats are also likely the origin of Ebola, Marburg and Nipah.


Mammalian Misdemeanours

There are two things you need to know about bats – (1) they are extremely adaptable and (2) extremely diverse. They are the only mammals capable of sustained flight and they can be found in all kinds of habitats from deserts to cities. And bats make up a quarter of all mammalian species – and we haven’t even discovered all the bat species that exist on Earth yet!


Reservoirs of Viruses

Bats do indeed host a lot of viruses, many of which can be transferrable to other species including humans (“zoonotic” viruses). And while most mammals carry viruses, in terms of the number zoonotic viruses hosted, bats are bested only by rodents. And in terms of zoonotic viruses per species, bats are in a league of their own, hosting 1.8 zoonotic viruses per species.  


How Do Bats Spread Viruses?

Scientists theorise that to preserve energy for flight bats have evolved in a way wherein their bodies discard bits of DNA floating where they shouldn’t be. And if these DNA bits – which would include viruses – are disposed while in flight, they can cover large areas and affect many other animals in the vicinity, thus spreading viruses far and wide.


Why Don’t the Viruses Kill the Bats Themselves?

The answer to this intriguing question is inconclusive. Some researchers point to their ability to generate large repertoires of naïve antibodies. Others suggest their high in-flight internal temperatures are to credit for their super-tolerance. Researchers have found that bats have unusual immune systems whose antiviral response have developed through natural evolution in a way that empowers their immune system to fight against viruses but not go into overdrive, as it happens in some humans.   


(BTW you might also want to read Why So Many New Diseases Start in China? and What Exactly is a Coronavirus?)


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