The symptoms are relatively "mild," says the zoo.

On Monday, the Denver Zoo announced that 11 African lions tested positive for COVID-19. This comes just 10 days after the zoo announced that two of its Amur tigers had tested positive.

It's not clear if the two groups of large cats' positive cases are connected.

"There have been a number of big cats to come down with COVID-19 at zoos throughout the country, including our two tigers, Yuri and Nikita," said Brian Aucone, senior vice president for life sciences for the zoo. "Fortunately, the vast majority have fully recovered, and the upside is that there’s an established knowledge base for us to draw from to help treat our animals. We’ve been in touch with other zoos that have also recently managed COVID cases in their big cats to inform the care we’re providing."

According to the zoo, zookeepers noticed the lions coughing, sneezing, acting lethargic, and dealing with nasal discharge. After nasal swab samples were sent to Colorado State University's Veterinary Diagnostic Laboratory, the positive results were confirmed by the U.S. Department of Agriculture's Veterinary Services Laboratories.

The animal care and veterinarians have described the symptoms as mild and they're closely monitoring and treating the lions as needed.

None of the lions were vaccinated against COVID-19, says the Denver Zoo.

"Our veterinarians are planning to vaccinate them along with the tigers as soon as more doses of the animal-specific Zoetis vaccine become available," said the zoo.

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