Bats In China Carry 400+ Coronaviruses With The Potential To Spill Over Into Humans : Goats and Soda The coronavirus outbreak in China seems like an unusual event. But scientists have found that similar viruses have been quietly jumping from bats into humans for years.
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New Research: Bats Harbor Hundreds Of Coronaviruses, And Spillovers Aren't Rare

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New Research: Bats Harbor Hundreds Of Coronaviruses, And Spillovers Aren't Rare

New Research: Bats Harbor Hundreds Of Coronaviruses, And Spillovers Aren't Rare

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  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript


Scientists say the current coronavirus outbreak in China was caused by what's called spillover. That's when an animal virus jumps into humans. And coronavirus spillovers were thought to be rare, but researchers working in China say they've found evidence that these spillovers have been happening all along. NPR's Nurith Aizenman reports.

NURITH AIZENMAN, BYLINE: We're going to start this story with a scene that NPR actually recorded three years ago in Malaysian Borneo.


KEVIN OLIVAL: OK. Mask is on. Gloves are on.

AIZENMAN: Kevin Olival is at the edge of a rainforest sitting in a makeshift outdoor biology lab. There are plastic chairs. And on a folding table, he places a small creature he's just caught - a female bat.


OLIVAL: It's OK, girl. It's OK, girl.

AIZENMAN: Olival is a disease ecologist with the nonprofit research group EcoHealth Alliance. He starts taking samples of the bat's body fluids.


OLIVAL: So we're getting the oral swab in the back of the throat. And I'm just holding her head between my two fingers with a leather glove on. Ooh, good one. There's definitely some sample on that swab.


OLIVAL: That was a reaction to a rectal swab.

AIZENMAN: He wants to check these samples for viruses. Bats are known for carrying some dangerous ones, particularly viruses that have the potential to kick off global outbreaks. So Olival and his colleagues are on the hunt for the next big threat. A few more swabs, and it's all done.


OLIVAL: And now she gets her special treat - a little bit of mango juice as a reward.

AIZENMAN: During that same period that NPR recorded this, Olival and his colleagues were also in the process of collecting samples from thousands of bats in China. And Olival says what they found is alarming.

OLIVAL: Yeah, so we found evidence for - in total from all the sampling we did in China - about - something like 400 new strains of coronaviruses.

AIZENMAN: That means 400 potential candidates to spark another outbreak. A coronavirus caused a massive outbreak in China back in 2002 to 2003 - Severe Acute Respiratory Syndrome, or SARS. And this current outbreak is from a SARS-related coronavirus. It gets worse. Scientists had thought spillovers were rare. Bat coronaviruses weren't generally capable of infecting humans. It took a lot of complicated steps. Step one, a bat coronavirus had to infect some animal species that had closer contact with people. Step two, while in that animal's body, the virus had to pick up new genetic code. But the sampling project found all those steps - not needed.

OLIVAL: What we showed was that SARS-related viruses in this bat population had the potential to go directly into human cells and do not need sort of that extra mutational step by infecting another host.

AIZENMAN: In other words, the path to sparking new outbreaks is potentially much more direct. For example, one of the coronaviruses they found was a very close genetic match for the SARS virus. So they put it in a petri dish with human cells, and it infected them. Olival says the fact that a bat coronavirus had the ability to infect human cells raised an obvious next question.

OLIVAL: Is there evidence that those viruses are actually infecting people?

AIZENMAN: So the researchers started taking blood samples from villagers in China who lived near some of the bat caves they'd been studying.

Hongying Li is an ecologist with EcoHealth Alliance. She says people were in the bat caves all the time. They were a popular local hangout.

HONGYING LI: When we went to the caves for sampling, we usually see people's, like, beer bottle and a, like, water bottle.

AIZENMAN: Li and her colleagues checked the villagers' blood for signs of recent infections with bat coronaviruses. And they did this again with people in some other rural areas. Both times...

LI: We find coronaviruses that's already spilled over into human population.

AIZENMAN: Multiple outbreaks that had gone undetected. Kevin Olival says this is a huge red flag.

OLIVAL: So the - sort of the signal was there that these SARS-related viruses were jumping into people even if they weren't causing any noticeable disease.

AIZENMAN: People might have had symptoms, but health authorities never picked up on it, which brings us to this current coronavirus outbreak. As soon as it started, EcoHealth Alliance's collaborators in China compared the new virus to the bat samples they'd collected. And they found an extremely close match.

OLIVAL: A viral taxonomist would probably call that the same virus species.

AIZENMAN: This new outbreak that's infected tens of thousands of people could have come directly from bats. Olival says the larger takeaway is clear.

OLIVAL: These bat SARS-related coronaviruses are actively spilling over in the human population.

AIZENMAN: Not all of them will spark deadly pandemics. But the more frequent these spillovers, the greater the chances.

Nurith Aizenman, NPR News.

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