White-tailed deer can transmit covid for five days after infection

A new Cornell University study finds North American white-tailed deer – shown in 2021 surveys of five states to have coronavirus infection rates of up to 40% – shed and transmit the virus for up to five days once infected.

“It’s a relatively short window of time in which the infected animals are shedding and are able to transmit the virus,” said Dr. Diego Diel, associate professor and director of the Virology Laboratory at Cornell’s College of Veterinary Medicine’s Animal Health Diagnostic Center.

The study, published in PLOS Pathogens, also identified that the virus develops and replicates in the deer’s respiratory tract, lymphoid tissues – including tonsils and several lymph nodes – and in central nervous system tissues.

“Virus replication in the upper respiratory tract – especially the nasal turbinates [nose structures] – is comparable with what is observed in humans and in other animals that are susceptible to the infection,” Diel said, “and I think that’s probably one of the reasons why the virus transmits so efficiently.” As with humans, the virus spreads between deer through nasal and oral secretions and aerosols.

The findings are critical for guiding epidemiological and immunological studies of the COVID-19 virus in wildlife to determine if deer can act as reservoirs that maintain the virus in nature independent of humans. Last year, researchers traced multiple introductions of the virus that causes COVID-19 from people into deer populations in several U.S. states.

Identifying target tissues where the virus replicates during infection could also provide useful information for hunters who harvest deer. While there is currently no evidence that humans have caught COVID-19 from deer, epidemiologists and others are concerned that hunters could become infected while harvesting an infected kill.

“Given the broad practice of deer hunting in the U.S., knowing the sites of virus replication is important to minimize the risks of exposure and transmission from these wild animals that could be potentially transmit the virus back to humans,” Diel said.