Study: COVID spread from deer to humans multiple times

The coronavirus spread from deer to humans at least a few times based on an analysis of samples taken from the animal, according to a new study. 

The analysis published Monday in the scientific journal Nature revealed that researchers found three possible cases of mutated variants of the virus from deer spreading to humans. Those cases appear to have originally stemmed from the virus spreading from humans to the deer and then mutating and spreading back to humans. 

The researchers, several of whom work for the Centers for Disease Control and Prevention or the Department of Agriculture, collected 8,830 respiratory samples from free-ranging white-tailed deer from 26 states and Washington, D.C., between November 2021 and April 2022. 

They identified 282 deer infected with COVID-19 and 34 different lineages of the virus in the samples collected, including those belonging to the alpha, gamma and delta variants that were more common earlier in the pandemic and the omicron variant that has dominated cases more recently. 

An analysis showed that at least 109 individual spillover events happened in which humans spread the virus to deer. That subsequently led to at least 39 incidences of deer-to-deer transmission and three cases of deer-to-human transmission. 

The delta and omicron variants were most commonly being reported among humans during the time that the researchers gathered the samples, but alpha and gamma were still being infrequently reported. 

Researchers from Ohio State University had warned in January 2022 of the possibility of the virus spreading from deer to humans. They found at least three different strains of the virus in more than 35 percent of the 360 wild white-tailed deer they studied in northeastern Ohio between January and March 2021. 

Two of the incidents of potential deer-to-human transmission occurred in North Carolina, and one happened in Massachusetts. 

The investigators were able to track down the three people who had the infections, but none reported being near deer in the month prior to getting COVID-19. They also said they were not near a zoo where a few lions were infected with the mutated strain. 

They concluded that the viruses circulating in the white-tailed deer population is coming from frequent spillover events from humans, and continued widespread surveillance of the deer population is needed to determine the evolution and distribution of the variants among deer. 

Additional research will also help evaluate if the deer are possibly a reservoir for the virus and their role in the ecology of the virus.