Photo/Illutration A waiting room is closed to prevent close contact between pet owners and animals at the Nara Animal Medical Center. (The Asahi Shimbun)

Cats infected with COVID-19 through human contact can rapidly spread the disease to other felines, a study has shown.

Researchers from the University of Tokyo and other institutions said they placed together three pairs of cats—one infected with the novel coronavirus and the other uninfected. Within six days, all six cats tested positive for COVID-19, the disease caused by the virus.

“The study demonstrated that cats can discharge infectious viruses,” said Ken Maeda, head of the Department of Veterinary Science with the National Institute of Infectious Diseases, who is well-versed in infectious diseases among animals.

“What is taking place now is owner-to-cat transmission,” he said. “Cat owners who are infected or suspect they have been infected with COVID-19 should take measures to keep their animals safe.”

COVID-19 is believed to have originated in bats.

In the U.S. state of New York, house cats and tigers with coughs and other symptoms have been found infected with the virus. They are all believed to have caught the virus from humans.

However, little has been known about the proneness of cat-to-cat transmissions.

In the cat experiment, Yoshihiro Kawaoka, a professor of virology with the University of Tokyo’s Institute of Medical Science, and other researchers took daily samples from the noses of three cats that had been exposed to the virus from a COVID-19 patient.

They tested the samples for the presence of the virus that could be transmitted to cultured cells.

Within three days, the virus was confirmed in all three cats.

On the day following exposure to the virus from a human, each cat was housed in a cage with an uninfected cat.

The virus was found in the noses of the three cage mates on the third day at the earliest and sixth day at the latest.

The research team said none of the six cats showed symptoms of infection or anomalies in body temperature and weight. The virus continued to be detected for four to six days.

When tested on the 24th day, all six cats were found to have IgG antibodies, which attack viruses.

Polymerase chain reaction (PCR) testing for COVID-19 determines the existence of any genetic material attributable to the novel coronavirus.

Positive test results could be caused by remnants of the virus that are no longer able to infect cells, so the PCR procedure cannot be used to establish if the virus is contagious.

Cultured cells were used in the latest study to confirm the presence of a contagious virus. While transmission occurred within several days, the cats retained the virus only for several days.

There has so far been no reported case of COVID-19 transmission from pets, including cats, to humans.

“Proneness to COVID-19 infection differs depending on the animal species, but at least (we know) feline animals are prone to catch the virus,” Kawaoka said.

“It cannot be ruled out that a pet animal in close contact with an infected human is potentially also infected (with COVID-19),” the Japan Veterinary Medical Association said in a statement released May 1 in response to overseas reports of infected cats and other animals. “The most essential thing for pet owners is to take solid measures for preventing transmission.”

The statement also advises owners to keep their pets indoors to prevent transmission outdoors between cats.

The research results were published online May 14 in the New England Journal of Medicine, a U.S. medical journal.

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