A tiger at the Bronx Zoo has tested positive for the new coronavirus, in what is believed to be the first known infection in an animal in the US or a tiger anywhere, a zoo spokesman said.

Key points: Seven animals have fallen ill at the Bronx Zoo in New York City

Seven animals have fallen ill at the Bronx Zoo in New York City All the animals were in contact with the same worker

All the animals were in contact with the same worker This is believed to be the first known infection in a tiger

The four-year-old Malayan tiger named Nadia — and six other tigers and lions that have also fallen ill — are believed to have been infected by a zoo employee who wasn't yet showing symptoms, the zoo said.

The first animal started showing symptoms on March 27, and all were doing well and expected to recover, said the zoo, which has been closed to the public since March 16 amid the surging coronavirus outbreak in New York.

"These are extremely hard days for all of us — no matter where we live and work," zoo director Jim Breheny said in a statement.

"We will ensure that whatever we can learn from these circumstances will be used to better understand and combat this disease."

The finding raises new questions about transmission of the virus in animals.

The US Department of Agriculture, which confirmed Nadia's test result at its veterinary lab, said there were no known cases of the virus in US pets or livestock.

"There doesn't appear to be, at this time, any evidence that suggests that the animals can spread the virus to people or that they can be a source of the infection in the United States," Dr Jane Rooney, a veterinarian and a USDA official, said in an interview.

The USDA said on Sunday it was not recommending routine coronavirus testing of animals, in zoos or elsewhere, or of zoo employees.

Still, Dr Rooney said a small number of animals in the US had been tested through the USDA's National Veterinary Services Laboratories, and all those tests came back negative except Nadia's.

The coronavirus outbreaks around the world are driven by person-to-person transmission, experts say.

According to data from Johns Hopkins University, the US has a total of 337,072 confirmed cases, and 9,619 deaths with the majority being in New York City.

There have been a handful of reports outside the US of pet dogs or cats becoming infected after close contact with contagious people, including a Hong Kong dog that tested positive for a low level of the pathogen in February and early March.

Hong Kong agriculture authorities concluded pet dogs and cats could not pass the virus to human beings, but could test positive if exposed by their owners.

Some researchers have been trying to understand the susceptibility of different animal species to the virus, and to determine how it spreads among animals, according to the Paris-based World Organisation for Animal Health.

The American Veterinary Medical Association and the Federal Centres for Disease Control and Prevention (CDC) have been recommending out of an abundance of caution, people ill with the coronavirus should limit contact with animals.

In general, the CDC also advises people to wash their hands after handling animals and do other things to keep pets and their homes clean.

At the Bronx Zoo, Nadia, her sister Azul, two Amur tigers and three African lions developed dry coughs, and some of the cats exhibited some wheezing and loss of appetite, Dr Paul Calle, the zoo's chief veterinarian said.

He said the zoo conducted the coronavirus test to be thorough.

Only Nadia was tested because it takes anaesthesia to get a sample from a big cat. Her temperature was taken at the same time, and it was normal, Dr Calle said.

The seven sickened cats live in two areas at the zoo, and the animals had contact with the same worker, who was doing OK, zoo officials said.

AP/Reuters