Over 80% of the deer tested positive for the virus.

According to a study conducted by researchers at Penn State University, Iowa’s population of white-tailed deer have contracted the coronavirus, and apparently at a disconcerting rate. The researchers took lymph node samples from both captive and free-roaming deer, all of whom are tracked through a pre-existing wildlife monitoring program. These samples, gathered between April of 2020 and January of 2021, showed that roughly 80% of the state’s deer population had been infected.

It’s been known for a while that the coronavirus is capable of spreading to non-human animals, and in fact, multiple animals both in the wild and in captivity have come down with full cases of COVID-19. However, the researchers found this new spike in deer infections disconcerting, as if the virus continues to proliferate outside of human intervention, it may become much more difficult to eliminate entirely.

“In principle, SARS-CoV-2 infection of an animal host could result in it becoming a reservoir that drives the emergence of new variants with risk of spillback to humans,” the researchers explained in their study.

Even if humanity finally reached herd immunity against the current iteration of the coronavirus, it could, in theory, continue to mutate in wild deer hosts and eventually make its way back to humanity in a potentially worse form. “Animal reservoirs can provide a refuge outside of a largely immune/vaccinated human population and thus represents a looming threat of reemergence into humans.”

“Given the social and economic importance of deer to the U.S. economy, even while experimental evidence suggest that SARS-CoV-2 infected deer remain largely asymptomatic, the clinical outcomes and health implications of SARS-CoV-2 infection in free-living deer are unknown and warrant further investigation,” the researchers concluded.