Snow Leopard at Illinois Zoo Dead After Contracting COVID-19: He 'Will Be Missed'

Joel Sartore

A snow leopard at an Illinois zoo has died after contracting COVID-19.

A resident of the Miller Park Zoo in Bloomington, 11-year-old Rilu, recently died "after struggling with COVID-induced pneumonia," the park shared on social media Thursday alongside a set of photographs shot by Joel Sartore.

"Rilu's personality and beauty will be missed by guests and staff, but he will not be forgotten," the caption on their post said, going on to remind visitors that "masks are required at all indoor spaces at Miller Park Zoo."

The heartbreaking update came one day after the zoo announced that more than one of their big cats were "exhibiting symptoms again."

"The first cat began coughing and had a raspy respiration beginning on November 20. The other four cats are still under veterinary treatment," they wrote, also including a statement from zoo superintendent Jay Tetzloff: "It is our obligation to do everything we can do for the animals here at the Miller Park Zoo."

Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human-interest stories.

RELATED: 3 Snow Leopards Die from COVID Complications at Nebraska Zoo: "Truly Heartbreaking"

Over the weekend, Sartore shared a video of a snow leopard on his own Instagram account, pleading with his followers, "If you haven't received a vaccination and booster yet, please do so. It's more than just human lives that are at stake."

"Snow leopards are proving extremely susceptible to the disease, and it's often fatal," he said.

In their post announcing the sad news of Rilu's death, Miller Park Zoo also shared that Rilu, whom the facility acquired in 2011, "produced seven living offspring that are now part of the Species Survival Plan (SSP)" and, as a result, "made the Miller Park Zoo one of the leading institutions in the world in producing Snow Leopard cubs."

While a snow leopard's life expectancy is generally 10 to 12 years in the wild, they can survive up to 22 years in captivity, according to the Snow Leopard Trust.

RELATED VIDEO: CEO of The Humane Society of the U.S. Says Pets "Are Not Carriers" of the Coronavirus

Rilu is the snow leopard to die after contracting COVID. In October, a 2½-year-old snow leopard died at the Great Plains Zoo in South Dakota after showing symptoms. The cat named Baya first exhibited symptoms one day after a tiger named Keesa "tested positive for the virus that causes COVID-19."

Baya experienced "a rapid decline of respiratory function" before she passed away at the zoo in Sioux Falls.

The following month, a trio of snow leopards — named Ranney, Everest, and Makalu — died from COVID-19 complications at the Lincoln Children's Zoo in Nebraska.

The Centers for Disease Control and Prevention state that some animals worldwide have been infected with the virus that causes COVID since the pandemic began, typically after close contact with people with COVID. The agency states that the risk of pets spreading COVID to humans is low, but humans with COVID should protect pets by isolating themselves away from their animals until they are healthy.

As information about the coronavirus pandemic rapidly changes, PEOPLE is committed to providing the most recent data in our coverage. Some of the information in this story may have changed after publication. For the latest on COVID-19, readers are encouraged to use online resources from the CDC, WHO and local public health departments. PEOPLE has partnered with GoFundMe to raise money for the COVID-19 Relief Fund, a GoFundMe.org fundraiser to support everything from frontline responders to families in need, as well as organizations helping communities. For more information or to donate, click here.