Haseltine also touched upon the next much-discussed possibility, which is that the omicron variant emerged from a process known as reverse zoonosis — that is, a situation in which a virus that originated in another animals jumps to humans, then back to animals, and then back to humans again. The COVID-19 pandemic originated from the first step of that process (jumping from an animal, probably a bat or a pangolin into humans), and the hypothesis is that the virus somehow jumped from a human to an animal and then back to a human.

Indeed, the SARS-CoV-2 virus has proved troubling adept at infecting animals that regularly come into contact with humans. The mink farming industry has taken a hit (quite possibly a fatal one) because of COVID-19 infecting huge numbers of the animals that are raised for their fur to feed the fashion industry. Likewise, the virus has infected dogs and cats, and American deer. Zoo animals like lions, giraffes and two-toed sloths have also gotten sick. While there is no evidence that the SARS-CoV-2 strains that entered these animals have managed to reinfect humans, that does not mean this would be impossible.

Not everyone buys that the omicron variant could have emerged that way. Trevor Bedford, a computational virologist and professor at the Fred Hutchinson Cancer Research Center in Seattle, told NPR that he doubts the omicron variant started in an animal because he does not see residual genetic material from those animals in its genome, but instead an insertion of human RNA. This “suggests that along [omicron’s evolutionary] branch, it was evolving in a human.”