Biologists and wildlife-rehabilitation volunteers are being warned not to handle bats during the COVID-19 pandemic to reduce the possibility of infecting millions of the flying mammals in North America.

The Canadian Wildlife Health Co-Operative (CWHC) is about to recommend the suspension of fieldwork involving bats, said University of Winnipeg biologist Craig Willis, one of the wildlife disease experts developing this new advice.

The U.S. Fish and Wildlife Service has made a similar recommendation to American bat biologists.

While the chance of an infected biologist passing on COVID-19 to a bat is remote, the result would be disastrous, Willis said.

The fear is millions of North American bats could become hosts for COVID-19, which is caused by a coronavirus similar to those present in Asian bats, he said.

"Even though the risk is low, I think the consequences for public health, but also bat conservation and people's opinions of bats, would not be great. So people are just being extra, extra careful," Willis said in an interview.

"We know that this virus can infect a range of species, or at least it appears that way. The question of course is … if it did spill back into bats or other wildlife, we would end up with another wildlife reservoir that could in turn pass it back to people.

"That would make eradicating it from North America, or Europe for that matter, extremely difficult, if not impossible."

A big brown bat hangs in a hibernaculum. University of Winnipeg biology professor Craig Willis, who studies and tracks bats, is calling on the public to help researchers monitor bat populations this spring and summer. (Mary-Anne Collis)

SARS-CoV-2, the formal name of the coronavirus that causes COVID-19, has genetic similarities to a coronavirus found in Asian horseshoe bats.

The theory is those bats transmitted the virus to another species, where it evolved into the micro-organism that has so far killed more than 100,000 people and sickened nearly two million.

"We may never know actually … where this thing came from," Willis said.

Nonetheless, Willis said it's very likely that North American bat species, such as the little brown bat, could carry this new coronavirus.

"We know that our bats in North America carry coronaviruses, as many other species do. But this new one that's making so many people sick and causing such problems for our public health system — that one certainly isn't in our bats," he said.

"But there are other viruses that are in all sorts of wildlife, and I think one of the things that happened over the course of my career is we've started to recognize that people studying wildlife should probably do a little bit better job of wearing personal protective equipment when we're working with our animals."

The shortage of gloves, masks and other personal protective equipment for health-care workers means that equipment should not be used by biologists right now.

"It's very important to keep it in reserves for our frontline public health people. So that's also one of the reasons we're recommending not handling bats at the moment," Willis said.

A bat with white-nose syndrome, a fungal infection that has killed millions of bats across North America. Researchers have found the fungus can weaken bats' robust immune systems and allow them to shed more viruses. (U.S. Fish and Wildlife Service)

The novel coronavirus may not hurt a healthy North American bat, Willis said. As highly social creatures that congregate in huge numbers, bats have evolved very strong immune systems that can tolerate the presence of many pathogens, including a number of coronaviruses, he said.

Nonetheless, Willis and colleagues at the University of Saskatchewan found evidence the new coronavirus could harm North American bats already weakened by white-nose syndrome, a fungal disease that has killed millions of bats on this continent.

"We looked at levels of the naturally occurring coronavirus that our little brown bats carry around. It doesn't make us sick, it doesn't appear to make the bat sick. But when we looked at bats that were suffering from white-nose syndrome, they were expressing about 60 times as much virus as healthy, controlled bats," Willis said. "That's a bit of a worry."

The transmission of viruses from animals to people is a consequence of wildlife habitat loss, where human development pushes into what used to be natural areas, Willis said.

Wildlife markets that confine stressed animals within a small space present a perfect opportunity for pathogens to jump from one species to another, he said. This risk is also increased by climate change, as animals move into environments that were once inhospitable to them.

Willis is encouraging Canadians in rural areas to help researchers keep track of bat populations, especially now that the pandemic has sidelined biologists.

"Now that we're not able to go out and do fieldwork, it would be amazing if people can help us count their bats," he said, noting the mammals are starting to emerge from their hibernacula, which include bat houses on private properties.

"That's something people can do. And it's really fun to do with your kids as a science project, [for] your home schooling."

Willis warned rural residents not to violate public-health advisories against travel or to wander onto other people's property.

Some of Canada's bat biologists maintain a citizen-science website at batwatch.ca.