COVID-19 Variants Evolve 3x Faster in Deer Than Humans

A study has revealed that COVID-19 viral variants undergo evolution approximately three times more swiftly in deer than in humans. This finding emerges from a study that observed over 30 instances of COVID-19 infections in white-tailed deer in the US, attributed to human introduction. The study is published in the Nature Communications (1^✔ ✔Trusted Source
Accelerated evolution of SARS-CoV-2 in free-ranging white-tailed deer

Go to source). Scientists collected 1,522 nasal swabs from free-ranging deer in 83 of the state’s 88 counties between November 2021 and March 2022. More than 10 percent of the samples were positive for the SARS-CoV-2 virus, and at least one positive case was found in 59 percent of the counties in which testing took place. “We generally talk about interspecies transmission as a rare event, but this wasn’t a huge sampling, and we’re able to document 30 spillovers. It seems to be moving between people and animals quite easily,” said Andrew Bowman, associate professor of veterinary preventive medicine at The Ohio State University.

Deer's Role in COVID-19 Virus Evolution

“And the evidence is growing that humans can get it from deer -- which isn’t radically surprising. It’s probably not a one-way pipeline,” he added. However, no substantial outbreaks of deer-origin strains have occurred in humans. How the virus is transmitted from humans to white-tailed deer remains a mystery. Yet the combined findings suggest that the white-tailed deer species is a reservoir for SARS-CoV-2 that enables continuing mutation, and that the virus’ circulation in deer could lead to its spread to other wildlife and livestock. Beyond the detection of active infections, researchers also found through blood samples containing antibodies -- indicating previous exposure to the virus -- that an estimated 23.5 percent of deer in Ohio had been infected at one time or another.The 80 whole-genome sequences obtained from the collected samples represented groups of viral variants: the highly contagious delta variant and alpha.

The analysis revealed that the genetic composition of delta variants in deer matched dominant lineages found in humans at the time, pointing to the spillover events, and that deer-to-deer transmission followed in clusters, some spanning multiple counties. The study also suggested that COVID-19 vaccination is likely to help protect people against severe disease in the event of a spillover back to humans. An analysis of the effects of deer variants on Siberian hamsters, an animal model for SARS-CoV-2 studies, showed that vaccinated hamsters did not get as sick from infection as unvaccinated animals. Thus, the variants circulating in deer are expected to continue to change.

“Not only are deer getting infected with and maintaining SARS-CoV-2, but the rate of change is accelerated in deer --potentially away from what has infected humans,” Bowman said.

Reference:

1. Accelerated evolution of SARS-CoV-2 in free-ranging white-tailed deer - (https://www.nature.com/articles/s41467-023-40706-y)

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