By Steve Gorman

LOS ANGELES (Reuters) – Two gorillas at the San Diego Zoo have tested positive for COVID-19 after exhibiting symptoms of the disease, California’s governor said on Monday, in what is believed to be the first known transmission of the virus to apes.

Governor Gavin Newsom, in his latest coronavirus update for the state, said the source of the gorillas’ infection was still under investigation to determine whether the virus was transmitted between animals or from humans to the apes.

A statement posted on the San Diego Zoo Safari Park website said the gorillas were suspected of having contracted infection “from an asymptomatic staff member,” despite following all COVID-19 safety precautions recommended by the U.S. Centers for Disease Control and Prevention.

Zoo authorities initiated testing of fecal samples of the park’s gorillas after two of the apes began coughing last Wednesday, and preliminary results two days later found the presence of the virus “in the gorilla troop,” the statement said.

The U.S. Department of Agriculture National Veterinary Services Laboratories confirmed the positive results on Monday.

“The test results confirm the presence of SARS-CoV-2 in some of the gorillas and does not definitively rule out the presence of the virus in other members of the troop,” it said.

“Aside from some congestion and coughing, the gorillas are doing well,” Lisa Peterson, executive director of the San Diego Zoo Safari Park, said in the statement. “The troop remains quarantined together and are eating and drinking. We are hopeful for a full recovery.”

Gorillas are members of the family of primates known as the great apes, or hominids, that also include orangutans, chimpanzees and humans.

The coronavirus has also been found in a number of other wild-animal species in captivity, including several lions and tigers at the Bronx Zoo in New York and four lions at the Barcelona Zoo in Spain.

But the gorillas in San Diego are believed to mark the first known case of infections confirmed in apes. The virus also has shown up in a number of household dogs and cats.

Last month, the USDA said it had confirmed the first known case of the coronavirus in an animal in the wild, a mink, following an outbreak among farmed minks that killed 15,000 of the animals.

(Reporting by Steve Gorman in Los Angeles; Editing by Leslie Adler and Peter Cooney)