(CNN) — The surge of COVID-19 in California has just gotten even worse, after at least two gorillas at the San Diego Zoo became infected with COVID-19, the zoo and Gov. Gavin Newsom said Monday.

Three animals are currently showing symptoms of the virus, and it is suspected that they were infected by an asymptomatic staff member, according to a press release.

This is the first known instance of coronavirus in great apes, the zoo said, though previous research has shown that some non-human primates are susceptible. The gorillas live as a family, so it is assumed that all members have been exposed, zoo officials say.

It started last Wednesday, when two zoo gorillas began coughing. A preliminary test within the group showed presence of the virus on Friday, and the US Department of Agriculture’s National Veterinary Services Laboratory confirmed the positive results Monday.

It is unknown whether the gorillas will have any serious reaction, the zoo said, but they are being closely monitored.

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

San Diego Zoo has been closed to the public since early December.

California has become an epicenter of COVID-19, with 4,971 patients in the ICU on Monday. Meanwhile, across the country, the total number of Americans with the virus surpassed 22 million over the weekend, according to Johns Hopkins University data, and more than 375,000 have died.

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