This report on Gizmodo describes a study of Covid-19 infections amongst household pets of people who were themselves infected with the coronavirus.

It has been known for a while that some pets (dogs, cats and members of the weasel family) can get infections of Covid-19. Generally, these infected animals only exhibit minor symptoms, and do not infect humans (although mink, part of the weasel family, show more severe symptoms and can infect humans). What was not so clear was how often these pets were getting infected.

The new study shows that infections of pets by humans is actually fairly common.

The Gizmodo article is rather dismissive of the risk, because of the fact that cats and dogs do not infect humans. So what happens when a new variant evolves, which can make the leap from pets back to humans? This is not such a stretch of the imagination, given the constant parade of new mutant coronavirus types, and the fact that such a mutant variant first made the leap from animals to humans in the first place.

If such a variant (or even several such variants) emerges, the disease will be much harder to control, because there will be a reservoir of infections amongst unvaccinated pets. Mass culling of household pets will be very strongly resisted by pet owners, so vaccination of pets seems the only option, and we do not yet have Covid-19 vaccines for dogs and cats.

This new data suggests that the threshold for achieving herd immunity will be even tougher than previously thought; a 70% vaccination rate is simply not going to cut it.