The Evolution of SARS-CoV-2 and Influenza A Virus at the Human–Animal Interface (opens in a new tab)

In the wake of the COVID-19 pandemic, there has never been stronger universal recognition of the need for more studies of virus spillover at the human–animal interface to combat the growing threat of emerging zoonotic diseases. We learned a great deal from the 2009 H1N1 pandemic and prior influenza pandemics about the molecular changes that allow certain viruses to overcome these host-restriction barriers. Moreover, large-scale genomic sequencing is beginning to expose the high frequency of virus spillover between humans and animals and refine our understanding of its bidirectional nature. For example, it turns out humans actually transmit more flu to pigs than the reverse, turning swine into breeding grounds for new chimeric viruses with genetic components from humans, birds, and pigs. Intensified surveillance during the COVID-19 pandemic revealed that reverse zoonosis transmission from humans to animals occurs not only in livestock and pets with high contact rates but also to wildlife, including white-tailed deer, exposing blind spots in our understanding of the human–animal interface for pandemic pathogens.