How do bats live with so many viruses?

Bats have a pretty bad reputation, which is not surprising considering the number of pathogens they carry that can infect humans. Rabies, Nipah, Hendra, Ebola and Marburg are all viruses carried by bats that can cause serious disease in humans. Marburg virus and some strains of Ebola virus can kill up to 80-90% of humans infected.

Like Ebola virus in Africa and the Nipah virus in Asia, the new coronavirus — 2019-nCoV — appears to have originated in bats. Chinese researchers took samples of the coronavirus from patients in Wuhan, the city in central China where the outbreak was first detected.

They compared the genetic sequence of the new coronavirus — 2019-nCoV — to a library of known viruses and found a 96% match with a coronavirus found in horseshoe bats in southwest China.

Many other researchers think this new coronavirus spread from bats to humans, with a possible stop with another animal in between. It’s happened with other coronaviruses. In the case of the SARS (Severe Acute Respiratory Syndrome) outbreak, from 2002-2003, a bat coronavirus jumped to civets, a member of the mongoose family, and was sold to people as food at markets. The MERS (Middle East Respiratory Syndrome) outbreak, first detected in 2012, was caused by a coronavirus that jumped from bats to camels to people who maybe drank raw camel milk or ate undercooked meat.

So why do so many infectious diseases emerge from bats?

First, bats carry a great variety of viruses — and the viruses they carry seem more likely to spread to people. Scientists aren’t completely sure why, but it may have to do with the families of viruses that some bats tend to carry. There are over 130 different kinds of viruses found in bats.

Second, bats and humans have a lot of contact. There are billions of bats and more than 1,300 different species living on every continent except Antarctica. They roost in huge, crowded colonies together. Members of different bat species share caves and hollowed out trees in groups up to the millions, where viruses can pass easily between them through close contact with each other.

They have long lifespans relative to their size, and can live for more than 30 years. So there’s a long time for them to be persistently infected with the virus and shed it into the environment. Bat viruses are shed through urine, feces and saliva. Outbreaks of Nipah virus in Bangladesh have been linked with date palm sap collected from trees that bats had licked or urinated on.

Meanwhile, you might be wondering: Why aren’t the bats themselves affected by the viruses? It turns out that the answer to that question has to do with the bat’s status as the world’s only flying mammal.

During flight, a bat’s body temperature spikes to over 100 degrees Fahrenheit. Its heart rate can surge to more than 1,000 beats per minute. For most land mammals, these are signals that would trigger death. But bats live it every day.

It seems that bats have developed special immune systems to deal with the stress of flying. Their bodies make molecules that other mammals don’t have, which help repair cell damage. And their systems don’t overreact to infections, which keeps them from falling ill from the many viruses they carry (and also prevents conditions like diabetes and cancer).

This shows that it’s not always the virus itself but the body’s response to the virus that can make us sick.

But let’s be clear: it’s not the bats’ fault that people are getting diseases. They’ve just sort of coevolved with these viruses and these bugs that basically don’t cause them any harm. The problem is when the viruses jump to new species. And it’s human activity that makes that likely to happen.

And bat researchers stress that bats aren’t just a possible source of viruses. They play a hugely important role in Earth’s ecosystem. They eat tons of insects and pollinate plants and disperse seeds for hundreds of plant species. And they’ve found a way to coexist with the viruses they carry — which means that even though bats may be the source of viruses that affect humans, they could also be the source of potential therapies if we study their immune systems.

Furthermore, most of these are emerging diseases that have rudely burst onto the scene over the past 50 years (although some argue they have been around a lot longer, but weren’t diagnosed). But what is causing this rise in viral disease? It turns out that it is just as much their fault as it is ours.

Humans have started creeping into bat territory, especially in the tropics, which has led to an increased risk of contact with these animals. For example, in Malaysia, commercial pig farms were installed in bat inhabited forests which consequently led to the first human outbreak of Nipah, via pigs.

But don’t go hating on bats because of this- they’re incredibly important pollinators and they also eat mosquitoes. You win some, you lose some.

Check out my related post: What’s the difference between Wuhan’s virus, MERS and SARS ?


Interesting reads:

https://www.todayonline.com/world/how-do-bats-live-so-many-viruses

https://www.nytimes.com/2020/01/28/science/bats-coronavirus-Wuhan.html

https://www.npr.org/sections/goatsandsoda/2020/02/09/803543244/bats-carry-many-viruses-so-why-dont-they-get-sick

https://www.iflscience.com/plants-and-animals/why-do-bats-transmit-so-many-diseases/

https://www.sciencedaily.com/releases/2020/02/200210144854.htm

https://healthcareinamerica.us/what-makes-bats-the-perfect-hosts-for-so-many-viruses-3274c019bb4d

10 comments

  1. Whoa 😳!!!!!! This is batty!! I love bats 🦇 “you win some, you lose some”. 😷🤦🏼‍♀️😊 Bats~do your thing. Humans~do your thing. Everyone~have faith and play nice. ♥️

    Liked by 1 person

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