Scientists have found that SARS-CoV-2, the coronavirus that causes COVID-19, can spread like wildfire among white-tailed deer in parts of the US. While it’s still unclear whether the virus can jump from deers back to humans, the findings could have some worrying implications for the course of the pandemic.
In a new study, scientists tested a total of 283 white-tailed deer – 151 free-living and 132 captive – in Iowa from April 2020 through December of 2020 for SARS-CoV-2. They concluded that 33 percent of the animals were infected with the virus. Among the 97 samples taken specifically between November 23, 2020, and January 10, 2021, a shocking 82.5 percent were positive.
The research, which has not yet been peer-reviewed, was posted on the pre-print server bioRxiv earlier this month.
The overwhelming numbers, as well as the distribution of the cases, suggest that the virus spilled from humans to deers on multiple occasions and then spread prolifically through deer-to-deer transmission. Fortunately for the deer, the infections appeared to be asymptomatic and the animals were not suffering.
Previous studies have reached similar findings. In August, scientists published research that suggests up to 40 percent of wild deer living in Illinois, New York, Michigan, and Pennsylvania tested positive for antibodies against SARS-CoV-2.
Although it’s apparent that human-to-deer transmission and deer-to-deer transmission can occur, neither of the studies discovered whether deer-to-human transmission is possible. However, if the virus can jump from deers into humans then this has some worrying implications. Firstly, it raises the possibility that deer could act as a natural reservoir for the virus, silently harboring the infection and sparking new human outbreaks of COVID-19 in the future. Secondly, and perhaps most worryingly, it could foster the creation of new variants.
“In principle, SARS-CoV-2 infection of a non-human animal host could result in it becoming a reservoir that drives the emergence of new variants with risk of spillback to humans,” the paper reads.
This is all speculative for now and more research is needed, but the risk to humans is thought to be low. The US Department of Agriculture gave a statement to IFLScience in August that read: “Currently, there is no evidence that animals play a significant role in spreading SARS-CoV-2, the virus that causes COVID-19, to people. The risk of animals, including deer, spreading COVID-19 to people is low."
Deer are not the only concern. Researchers believe it's possible for many mammal species to contract the disease. So far, evidence of SARS-CoV-2 has been documented in cats, dogs, tigers, mink, and a bunch of other species.