A 4-year-old tiger named Nadia at the Bronx Zoo in New York City has tested positive for COVID-19, the Wildlife Conservation Society announced today (April 5). New York City has been one of the hardest hit areas by the coronavirus in the U.S.

This female Malayan tiger, along with six other big cats — including Nadia's sister Azul, two Amur tigers and three African lions — had all come down with a dry cough. Though these other cats weren't tested, the zoo is assuming they were also infected with SARS-CoV-2, the virus that causes COVID-19, due to their symptoms.

"We tested the cat out of an abundance of caution and will ensure any knowledge we gain about COVID-19 will contribute to the world's continuing understanding of this novel coronavirus," the WCS, which operates the zoo, said in a statement.

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A zoo caretaker with COVID-19 likely infected the cats before he or she developed any symptoms of the disease, the WCS said. Since then, preventive measures have been put into place for staff in order to prevent further exposure to the cats, the WCS said.

Though the infected cats have shown a decrease in appetite, they otherwise are doing well, the WCS said, describing the cats as "bright, alert and interactive with their keepers." Vets at the zoo are currently caring for, and monitoring, the sick cats. All are expected to recover, the statement said.

The four tigers with COVID-19 live in the Tiger Mountain exhibit, which also houses a male Amur tiger that has not shown any symptoms of COVID-19, the zoo said. In another exhibit called Wild Asia, a Malayan tiger and two Amur tigers also have not shown any symptoms. In addition, the other cats at the zoo, including the snow leopards, cheetahs, clouded leopard, Amur leopard, puma and serval, have not shown coronavirus symptoms.

Domestic cats have been infected with COVID-19 by their owners, Live Science previously reported . Cats seem to have a receptor protein on the outsides of respiratory cells that is similar to the human counterpart involved in SARS-CoV-2 infections. Called ACE2, this receptor protein is what allows the virus to break into these cells and multiply.

"The feline ACE2 protein resembles the human ACE2 homologue, which is most likely the cellular receptor which is being used by SARS-CoV-2 for cell entry," Steven Van Gucht, virologist and federal spokesperson for the coronavirus epidemic in Belgium, told Live Science previously.

In a recent report published online in the preprint journal medrXiv, Hualan Chen of Harbin Veterinary Research Institute, the Chinese Academy of Agriculture Sciences, described how SARA-CoV-2 was transmitted between cats in their respiratory droplets. Another paper, also published in medrXiv, found that of 102 cats tested in Wuhan, nearly 15% had antibodies to the virus, suggesting they can contract the virus from humans or other cats. No evidence has been found that cats can transmit the virus to humans, the authors of both studies noted.

These studies don't indicate whether big cats like lions and tigers have a similar receptor protein to domestic cats. "It is not known how this disease will develop in big cats since different species can react differently to novel infections, but we will continue to monitor them closely and anticipate full recoveries," the WCS said.

The WCS's Bronx Zoo, Central Park Zoo, Queens Zoo, Prospect Park Zoo and New York Aquarium have all been closed since March 16, the WCS said.

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Originally published on Live Science .