White-Tailed Deer in the US Shown to Transmit COVID-19
In a recent study led by the US Department of Agriculture (USDA), it has been found that white-tailed deer in the United States have transmitted the pandemic coronavirus, SARS-CoV-2, to humans on at least three occasions. The research also reveals that these deer have spread the virus extensively among their own population, with around a third of tested deer showing signs of prior infection.
The study, conducted by the USDA’s Animal and Plant Health Inspection Service (APHIS), supports previous findings that white-tailed deer can acquire the virus from humans, pass it on to other deer, and potentially transmit it back to humans. The implications of this suggest that the deer population could potentially serve as a reservoir for the virus, allowing it to adapt and return to humans in the form of new variants. These new variants may have the ability to evade immune protections gained from previous infection or vaccination.
Dr. Xiu-Feng “Henry” Wan, an expert in emerging infectious diseases at the University of Missouri who participated in the research, emphasizes the significance of the findings. Deer regularly come into contact with humans and inhabit areas close to human habitats, such as residential areas and waste disposal sites. Wan states that the potential for zoonotic diseases like SARS-CoV-2 to persist and evolve in wildlife populations poses unique public health risks.
Between late 2021 and 2022, the USDA, together with researchers and state partners, surveyed over 11,000 white-tailed deer across 26 states and Washington, DC. The results revealed that 31.6 percent of the deer had antibodies indicating prior infection with SARS-CoV-2, while 12.2 percent had detectable virus.
Additionally, the researchers collected approximately 9,000 respiratory samples from deer in the same locations and time period and sequenced the viral genomes of nearly 400 isolated SARS-CoV-2 viruses. An analysis of the genetic sequences showed at least 109 instances of spillover from humans to deer, with onward transmission within the deer population. The viruses observed in the deer encompassed multiple variants circulating among humans, including Alpha, Gamma, Delta, and Omicron. The genetic data also identified changes specific to the SARS-CoV-2 virus as it spread from deer to deer.
Interestingly, the genetic data suggested that the virus has also spilled back over from deer to humans in three instances. Two cases were reported in North Carolina, while one was identified in Massachusetts. Comparing the sequences of SARS-CoV-2 from deer to those isolated from humans, the viruses were found to be over 99.9 percent identical in the corresponding states. These findings have been published in Nature Communications.
Since the collection and analysis of this data, the APHIS has expanded its surveillance of SARS-CoV-2 in deer. While there is currently no evidence that deer play a significant role in the transmission of the virus, researchers are working to address various unknowns, including the mechanisms behind deer-to-human and human-to-deer transmission.
The ongoing study highlights the importance of understanding the potential role of wildlife in the transmission and evolution of infectious diseases. As the pandemic continues, further research and surveillance efforts will be crucial in managing and preventing future outbreaks.