According to the researchers, who have yet to publish their findings, discovering Omicron in deer raises the concern that new variations of the disease could breed within the deer population and then reinfect humans. After all, COVID-19 is a zoonotic virus, meaning it passed from animals to humans in the first case.

“You can imagine this could be a never-ending, perpetual cycle of deer constantly circulating the virus among themselves and picking up the new variants,” Suresh Kuchipudi, a veterinary microbiologist at Penn State who led the research team, told the New York Times.

Deer could be a particularly problematic vector for COVID. The animals roam widely and appear to be generally asymptomatic. Humans are inclined to interact with the seemingly docile creatures (more so than they are, say, with a rat or a mountain lion). Wild deer are also hunted and consumed in the U.S. Some states have already warned hunters to take extra precautions when handling deer carcasses, advising the hunters to wear rubber gloves or even face masks.

Although the researchers have found evidence that suggests the deer have transmitted the virus among one another, they have yet to find evidence that the virus has then passed from deer back to humans. (It’s possible deer contracted Omicron from humans.)

“We’re brand-new in finding these infections in the wild. And so that’s why we’re taking data, and that’s why we need to do more surveillance,” Kurt Vandegrift, a disease ecologist at Penn State and member of the research team, said to the Times.

The new research isn’t the first time scientists have detected COVID-19 within animals, or even within deer.

Last November, scientists in Iowa reported that 80% of samples taken from white-tailed deer in the state tested positive for the coronavirus. Meanwhile, vets have discovered plentiful COVID-19 cases in pets, gathering enough data to conclude that cats are more susceptible than dogs.

There have been some cases in which mutations of the COVID-19 virus appear to have reinfected humans, after appearing in animals. In 2020 scientists reported a mutant strain of COVID-19 had passed from minks to humans, prompting mass culls of the animal. In Denmark, authorities slaughtered over 17 million farmed minks, to prevent the viral spread.

Last month, authorities in Hong Kong rounded up and killed 2,000 hamsters after discovering COVID in one of the rodents, sold at a local pet shop, and blaming hamster-to-human infection for a rise in local COVID cases.

The government urged pet owners who had recently bought hamsters from the shop to offer up their pets to a euthanasia task force. Local animal lovers responded to the tiny reign of terror by creating an underground railroad for doomed hamsters.

So far, U.S. scientists have not suggested the culling of deer to quell the virus, though the scientists who discovered Omicron in the white-tailed population partnered with a team that was conducting herd thinning operations anyway—sterilizing young bucks—in order to catch and test the deer.

Researchers are concerned that the United States’ 38-million-strong population of deer could serve as a carrier for future outbreaks, but booster vaccines could be developed to tackle that issue. If it comes to that.