Accelerated evolution of SARS-CoV-2 in free-ranging white-tailed deer

Area of Science:

• Veterinary Virology
• Epidemiology
• Evolutionary Biology

Background:

• The zoonotic nature of SARS-CoV-2 necessitates understanding its ecology in non-human hosts.
• White-tailed deer in North America are frequently infected with SARS-CoV-2, highlighting their potential role in viral dynamics.

Approach:

• Utilized Bayesian phylogenetic methods to analyze SARS-CoV-2 evolution in white-tailed deer.
• Investigated multiple introductions from humans and subsequent deer-to-deer transmission.
• Quantified evolutionary rates and identified distinct mutational biases and selection pressures in deer.

Key Points:

• SARS-CoV-2 was introduced into white-tailed deer over 30 times in Ohio, with sustained transmission for 2-8 months across hundreds of kilometers.
• Alpha and delta variants evolved in deer at three times the human rate, driven by different evolutionary pressures.
• Deer act as reservoirs, allowing SARS-CoV-2 variants to evolve independently and potentially re-emerge.

Conclusions:

• White-tailed deer are significant reservoirs for SARS-CoV-2 evolution, exhibiting accelerated mutation rates and novel evolutionary trajectories.
• While no critical phenotypic changes were observed in experimental models, the long-term consequences of this accelerated evolution remain a concern.
• Continued surveillance and research are crucial to assess the risk of future SARS-CoV-2 evolution in deer populations and its implications for public and animal health.