If You Haven’t Thought About Coronavirus in Animals, You Should
Some research groups are focusing on the ACE2 receptor, a protein found on the surface of cells in many species. The spiked protrusions of the coronavirus allow it to bind to these receptors like a key in a lock and enter cells.
In 2020 a group of scientists compared ACE2 receptors of hundreds of vertebrates, mostly mammals, with human receptors to determine which species the virus might infect. (The ACE2 receptors of birds, reptiles, fish, and amphibians are not similar enough to ours to be of concern.)
“So far, the predictions have been very good,” Harris A. Levin, a UC Davis biologist and author of the study, said in an email. For example, scientists have predicted that white-tailed deer are at high risk of infection.
But some predictions turned out to be completely wrong: the article named farmed mink as a species of “very low” concern, and then in April 2020, the virus raged through the mink farms.
Indeed, ACE2 only offers a snapshot of susceptibility. “Viral infection and immunity are much more complex than just binding a virus to a cell,” Caitlin Sawatzky, a virologist at Tufts University, said in an email.
And out of nearly 6,000 mammalian species in the world, scientists have sequenced ACE2 receptors in just a few hundred of them, creating a biased data set. These sequenced species include model organisms used in experiments, species that carry other diseases, and charismatic zoo dwellers, not necessarily the animals people most often encounter.
“If the pandemic was caused by a squirrel, we would be like, ‘God, what is wrong with us? We didn’t even measure the basic biology of the squirrel,” Dr. Khan said.