Multiple spillovers from humans and transmission of SARS-CoV-2 with white-tailed deer

Jan. 26, 2022

A new study published by the Proceedings of the National Academy of Sciences of the United States of America provides strong evidence of extensive SARS-CoV-2 infection of white-tailed deer and human transmission. The analysis shows infection of deer resulted from multiple spillovers from humans, followed by efficient deer-to-deer transmission.

The discovery of widespread infection of white-tailed deer indicates their establishment as potential reservoir hosts for SARS-CoV-2, a finding with important implications for the ecology, long-term persistence, and evolution of the virus, including the potential for spillback to humans.

Many animal species are susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and could act as reservoirs; however, transmission in free-living animals has not been documented. White-tailed deer, the predominant cervid in North America, are susceptible to SARS-CoV-2 infection, and experimentally infected fawns can transmit the virus.

The geographic distribution and nesting of clusters of deer and human lineages strongly suggest multiple human-to-deer transmission events followed by subsequent deer-to-deer spread. These discoveries have important implications for the long-term persistence of the SARS-CoV-2 pandemic. Our findings highlight an urgent need for a robust and proactive “One Health” approach to obtain enhanced understanding of the ecology, molecular evolution, and dissemination of SARS-CoV-2.

The study was prompted by a recent report that 40% of free-living white-tailed deer in the United States had antibodies against SARS-CoV-2. The findings raise the concerning possibility of reverse zoonoses, especially in exurban areas with high deer density. The results also highlight the potential risks and considerable knowledge gaps associated with the continued molecular evolution of SARS-CoV-2 in animal hosts. Implementation of enhanced surveillance programs to define the magnitude of the deer reservoir problem and determine whether other reservoir species exist at the animal–human interface is warranted.

PNAS report

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