A four-year-old female Malayan tiger at the Bronx Zoo has tested positive for the coronavirus.
The tiger, named Nadia, is believed to be the first known case of an animal infected with Covid-19 in the US.
The Bronx Zoo, in New York City, says the test result was confirmed by the National Veterinary Services Laboratory in Iowa.
Nadia, along with six other big cats, is thought to have been infected by an asymptomatic zoo keeper.
The cats started showing symptoms, including a dry cough, late last month after exposure to the employee, who has not been identified.
There have been isolated instances of pets testing positive for the coronavirus elsewhere in the world, but experts have stressed there is no evidence they can become sick or spread the disease.
This coronavirus was first detected in humans in the Chinese city of Wuhan late last year.
The coronavirus (called Sars-CoV-2, which causes the disease Covid-19) is thought to have originated in wildlife and been passed to humans via a live animal market in Wuhan.
The pandemic has been driven by human-to-human transmission, but the infection of Nadia raises new questions about human-to-animal transmission.