The Nebraska Zoo announced in November of 2021 that the leopards had died of complications from covid-19, about one month after the animals had tested positive for the coronavirus. While scientists are still studying the effects of the virus on animals, members of several species have been infected and died in zoos around the world. Snow leopards are considered vulnerable to extinction, with just a few thousand estimated to be living in the wild.

Last month, the park said its animal keepers had “observed symptoms consistent with the virus in felids,” which can include coughing, fatigue and loss of appetite. They collected nose swabs and fecal samples, and the cats tested positive soon after, the zoo’s first cases. Two Sumatran tigers, Axl and Kumar, were also infected, but the zoo said Friday that they “have made a seemingly full recovery from their illness.” the zoo said. In a statement in October, the zoo said the infected animals were being treated with steroids and antibiotics, but it did not say whether they had been vaccinated. Zoetis, a former Pfizer subsidiary based in New Jersey, has provided an animal-specific coronavirus vaccine to zoos across the country.

Since April 2020, when a tiger tested positive for the coronavirus at the Bronx Zoo, dozens of animals in captivity in the United States have become infected. This month, the Denver Zoo reported the world’s first two coronavirus cases in hyenas, and the St. Louis Zoo found eight positive cases among its big cats, including in two snow leopards. It is possible for humans to infect cats with the coronavirus and for cats to pass it on to other cats, according to the Cornell Feline Health Center. However, the Cornell center said, there is not yet evidence that cats can infect people. The Food and Drug Administration classifies the risk for animal-to-people spread as low.