Why Don't Bats Get Sick Even Though They Carry Many Viruses? : Goats and Soda The winged mammal has a unique ability to carry viruses and not get sick from them. This tolerance may be a unique adaptation to flying.

Bats Carry Many Viruses. So Why Don't They Get Sick?

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Ebola in Africa, Nipah in Asia, rabies and mumps and now a new coronavirus spreading out from China - these are all diseases that likely got their start in bats. It turns out bats have a unique ability to carry viruses and not get sick from them. This tolerance may have developed millions of years ago as these animals evolved. NPR's Pien Huang reports.

PIEN HUANG, BYLINE: Chinese researchers compared the genetic sequence of the new coronavirus to a library of known viruses. They found a 96% match with a different coronavirus found in horseshoe bats in southwest China.

VINEET MENACHERY: They're too close in terms of their pure genetics to say that they're not related or that they didn't have a common ancestor.

HUANG: Vineet Menachery is a virologist at the University of Texas Medical Branch. He and other researchers think this new coronavirus spread from bats to humans, with a stop in between in a different animal. Investigators found traces of the virus in 22 stalls and a garbage truck at a live-animal market in the city of Wuhan, which was tied to many of the early cases. The animal in the middle is still a mystery. Some scientists think it's a pangolin. Linfa Wang, who studies bat viruses at Duke-NUS in Singapore, says it's easy to imagine how an animal could spread the virus to humans.

LINFA WANG: The animal can sneeze. The animal can urinate. If a human touches and blow your nose or whatever, then you've got it.

HUANG: It's happened before. For SARS, a coronavirus outbreak that started in 2002, a bat virus jumped to civets, which were sold as food at a market. For MERS, another coronavirus from 2012, a virus jumped from bats to camels and then to people, which raises the question, what is up with bats? Rebekah Kading researches emerging infectious pathogens at Colorado State University.

REBEKAH KADING: There's a lot of viruses we're finding in bats because there's a lot of bats out there.

HUANG: We're talking billions on Earth at any given time. They can also live for more than 30 years.

KADING: So there's a long time for them to be persistently infected with a virus and shed it into the environment.

HUANG: But here is their superpower. They don't seem to get sick from the viruses they hold. Bats are the only mammals that fly. And Linfa Wang at Duke-NUS thinks the tolerance to viruses comes from adaptations made millions of years ago, when bats first evolved to fly. In flight, he says...

WANG: Their metabolism goes crazy. And their heartbeats go to over 1,000 beats per minute.

HUANG: Their temperatures spike to over 100 degrees. They're burning a lot of energy, which creates toxins that damage their cells. These bodily changes would kill most mammals. But bats live it every day. Wang says it seems that bats have had to develop special immune systems.

WANG: Because as a flying mammal, as you can, you know, imagine - right? - they have the stress that we don't have.

HUANG: Their bodies make molecules that other mammals don't have that help repair cell damage. And their bodies don't overreact to infections, which helps prevent conditions like diabetes and cancer and also illness from the many viruses they carry. This is key, Wang says, because it's the body's response to a virus that can make us sick. Kevin Olival, a research scientist at EcoHealth Alliance, says, let's be clear. It is not the bats' fault that people are getting diseases.

KEVIN OLIVAL: They've just sort of coevolved with these viruses and these bugs that basically don't cause them any harm.

HUANG: The problem, he says, is when viruses jump to new species. And it's human activity that makes that likely to happen. In wildlife markets, like the one in Wuhan, Olival says animals that would rarely mix in nature come together. A bat in a cage could get stacked over a civet. Butchers could be handling animals without gloves.

OLIVAL: The way that we're coming into contact with these animals and hunting them and selling and trading them to a scale that, really, we haven't seen before.

HUANG: Olival says bats are hugely important to our ecosystems. They eat insects. And they pollinate plants and disperse seeds. And they found a way to coexist with the viruses they carry. He says we could learn a lot about our own immune systems and potential therapies by studying them. Pien Huang, NPR News.

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