Four more tigers and three lions at the Bronx Zoo in New York City have tested positive for the virus that causes COVID-19, the zoo announced Wednesday afternoon, following a National Geographic inquiry. This comes nearly three weeks after one tiger at the zoo was confirmed to have the virus and six other cats were said to be exhibiting symptoms.

The diagnosis of the tiger, named Nadia, represented “the first time, to our knowledge, that a [wild] animal has gotten sick from COVID-19 from a person,” Paul Calle, chief veterinarian for the Bronx Zoo, said April 5. The big cats likely contracted the coronavirus from an infected but asymptomatic zookeeper whose identity is unknown, Calle says: “It’s the only thing that makes sense.” Calle says.

The zoo has been closed to visitors since March 16. Initially it did not plan to test the other cats showing symptoms, because doing so would require sedation, which can be dangerous. But the U.S. Department of Agriculture subsequently updated an online database with information that a lion in New York had also been confirmed as testing positive for the virus on April 15. National Geographic contacted the Bronx Zoo seeking more information on April 22. And shortly thereafter the Wildlife Conservation Society, the nonprofit that runs the Bronx Zoo, issued a press release announcing that four additional tigers and three lions had tested positive. The zoo confirmed in the press release that the additional tests were done using fecal samples and did not require sedation.

It is not clear when the additional tests on the three lions and four tigers were conducted or when the zoo received the results; a zoo spokesperson did not respond to questions about the timing. The USDA did not respond to National Geographic’s request for comment by press time.

Several domestic animals have tested positive for SARS-CoV-2, the virus that causes COVID-19, including two cats in New York State—the first in the United States, the USDA announced today. A Pomeranian and a German shepherd in Hong Kong, as well as a domestic cat in Belgium, have also tested positive. The U.S. Centers for Disease Control and Prevention today issued new guidelines on the virus for pet owners, saying that while it does not recommend widespread testing at this time, it encourages cat owners to keep their cats indoors whenever possible.

Both wild and domestic cats had been known to susceptible to feline coronavirus—but until recently, it was unknown whether they could contract SARS-CoV-2. A new Chinese study has found that cats may be able to infect each other. Scientists now are rushing to learn what other species may be able to be infected by it.

A world first at the Bronx Zoo

After developing a dry cough in late March, Nadia, a four-year-old Malayan tiger, was tested for the virus on April 2, according to Calle. At that time Nadia’s sister, two Siberian tigers, and three African lions also had coughs and a loss of appetite. When Nadia started showing symptoms, the veterinary team did a number of diagnostic tests and blood work. “Considering what’s going on in New York City, we of course did the COVID testing,” Calle said. The team took samples at the zoo, after sedating Nadia. They sent the samples for testing to the New York State Diagnostic Laboratory at Cornell University and the University of Illinois College of Veterinary Medicine Veterinary Diagnostic Laboratory. It is not the same type of test that health care providers give to people, Calle said, “so there is no competition for testing between these very different situations.”

The zoo has all eight cats—one of which is not showing symptoms—under veterinary care and expects them to recover, the Wildlife Conservation Society statement says. While it’s becoming clear humans can pass the disease to some animals, there is currently no evidence that animals can spread the novel coronavirus to people, both the USDA and the Centers for Disease Control and Prevention say. (It’s believed the virus infecting humans likely developed from a very closely related coronavirus found in bats.)

What’s next?

Because this phenomenon is new, Calle said, there are many unanswered questions, including whether tigers and lions are more susceptible to coronavirus than other animals. None of the zoo’s other big cats—including snow leopards, cheetahs, a clouded leopard, an Amur leopard, and a puma—are showing symptoms.

The Bronx Zoo team has shared Nadia’s diagnostic information widely with the zoo and scientific community, Calle says. “I suspect that there are other cases, and now that we’re sharing this information I have a hunch other likely cases will turn up.”

Dan Ashe, president of the American Association of Zoos and Aquariums (AZA), commended Calle’s team for their quick action to test Nadia. The AZA accredits more than 200 zoos in the U.S., including the Bronx Zoo. Ashe said that the AZA has helped distribute USDA information that cautions about the potential virus transfer from humans to felids, and Bronx Zoo information about increased safety measures, including wearing masks and goggles to protect animals and keeping a distance of six feet whenever possible.

Ashe said that “If we’d known the keeper had COVID-19 they wouldn’t have been at work.” He said he believes human testing should be the priority because. “if [the virus] can go from people to big cats, the most important thing we can do is test the people.”

Although Ashe says he’s confident that accredited AZA facilities will continue to actively monitor the threat, he’s concerned for the big cats at the many substandard roadside zoos around the United States: “Anybody who has watched Tiger King, you think a facility like that would be able to respond in an appropriate way to information like this?” The majority of those zoos don’t have veterinarians on staff, and it’s unlikely tests would be done, Ashe said. And the cub-petting and close contact offered by these facilities is “is troublesome in best of circumstances,” he says, let alone at a time when the CDC and USDA are recommending maintaining distance among humans, and between humans and cats. (Read about the difference between accredited zoos, “roadside zoos,” sanctuaries, and “pseudo-sanctuaries” here.)