(CNN)Scientists have found SARS-CoV-2 spreads like, well, a virus among white-tailed deer and other wild animals in the United States.
People are the likely source, but that doesn't mean the virus can't evolve among these animals and then spill back into humans, and researchers are worried about what this spread means for the risk of future pandemics.
There's little doubt SARS-Cov-2, the virus that caused the ongoing pandemic, came from an animal -- almost certainly a bat. And the prevailing scientific opinion is that there as an intermediate host, an animal of some sort, that was infected by a bat or bats and then infected people.
It's also clear that people can infect animals. Pets such as cats, zoo animals such as gorillas and snow leopards and farmed mink can all be infected. Multiple cases have been reported, and evidence of changes in the viruses infecting mink have led to mass culls of those animals on fur farms.
The latest species to capture the attention of wildlife biologists are white-tailed deer. It's little surprise that farmed deer would catch the virus from people. Any visitor to a deer farm knows the animals behave like goats, shoving their wet noses into the pockets, hands and faces of human visitors or caregivers as they clamor for food and treats -- and setting themselves up for infection.
But how are wild deer catching it?
Viral spread among deer
"If somebody might bite an apple and throw it or even if I sneeze in a tissue and drop it," speculated Dr. Suresh Kuchipudi of the Animal Diagnostic Laboratory at Pennsylvania State University, who helped lead one study published earlier this month that found a third of deer they tested across Iowa between September of 2020 and January of 2021 showed evidence of infection.
Sewage has been found to carry the virus, so polluted water might be a source, he added, or people spitting or contaminating the environment in other ways. The deer may then spread the virus to one another.
"Keep in mind these are highly susceptible animals and while you do not know how much virus they need to be infected," Kuchipudi told CNN. "It raises the urgent question -- we know the deer are effectively transmitting virus among themselves, and then who are they giving it to?"
It's also possible another species could be picking up the virus from people and infecting deer.
"We don't know what's going on in our very own country and we need to find out," said Hon Ip of the United States Geological Survey in Wisconsin.
Viral hotspots among the rodents
Ip and colleagues tested animals they found around a mink farm that was the site of an outbreak in Utah and found skunks, mice and other animals were susceptible to a variety of coronaviruses.