COVID-19 transmitted between humans and deer multiple times, raising concerns of animal reservoir

COVID-19 has spread from humans to deer over 100 times, circulating widely in the deer population.
In deer, COVID-19 continued mutating, resulting in at least 3 instances where mutated strains spread back to humans.
Deer interacting closely with humans creates unique public health risks of new concerning variants.
Continued monitoring of animal populations is critical to understand COVID-19 persistence and evolution.
Preventing COVID-19 spread between species is important to avoid undermining immunity and vaccine efficacy.