But to determine when and in whom the mutations first appeared would require even more samples of the virus from farm workers, local residents and ferrets, collected before and after the outbreak. “That data doesn’t exist,” said Arinjay Banerjee, a virologist at the University of Saskatchewan.
Throughout 2020, testing was difficult for Americans, and very few patient samples were sequenced. Animal surveillance is even worse; Until this spring, federal officials had explicitly advised against routine animal testing for the virus.
“Large-scale testing was not available, then there was a shortage of certain supplies,” Dr. Behravesh said. “So we didn’t want to have, you know, a frenzy for animal testing.”
Without further samples, the possibility that the variant emerged in humans and then spread to ferrets cannot be ruled out, the scientists said.
A bigger puzzle is how the taxman and his wife got it. The most likely possibility, some experts say, is that the variant was circulating more widely in the population than is known, and that the couple contracted it from another infected person.
Another more speculative possibility is that they picked up the variant from another animal. “Insect taxonomists deal with other dead animals,” said Linda Saif, a virologist and immunologist at Ohio State University.
But because cases were discovered “weeks to months” after both fell ill, testing any animals they may have come into contact with “is not feasible or indicated,” says Lynn Sutfin , a spokesperson for Michigan DHHS, said.