Outside of a laboratory, infection depends primarily on the inhalation of virus particles from an infected person, and normal contact does not necessarily lead to infection of the animals. In the laboratory, ferrets have been shown to be susceptible to infection with the virus and spread it to other ferrets.
However, Tufts scientists reported in an as-yet-peer-reviewed article that in a house with 29 pet ferrets and two people with Covid, not one ferret was infected with the virus.
The 29 ferrets roamed around the house, and both adult humans were sick enough with Covid to show symptoms that there was ample opportunity for infection. Kaitlin Sawatzki, a virologist at Tufts University and one of the authors of the ferret paper, said, "Isn't that incredible? It was a beautiful natural experiment."
The researchers concluded that there may be genetic barriers to infection that can be overcome in a laboratory with concentrated doses of the virus. Minks, which belong to the same family as ferrets, appear to be very easily infected and develop the disease. Researchers have also reported on transmission from animals to humans on mink farms in the Netherlands in an as-yet-peer-reviewed article. Dr. Sawatzki said the paper shows "very strong evidence of multiple independent mink-to-human transmission events".
Colorado state researchers advise keeping cats indoors, especially if someone in a household is infected, because they could spread them to other cats. If a person with Covid needs to be hospitalized and has pet cats, the cat's caretakers should know how they would do with a person.
The infected cats who showed immunity said Dr. Bosco-Lauth, animals infected through contact with other cats were not infected by pipettes. And she said the immune response was stronger than some other laboratory animals, although it was completely unknown how long that protection could last.