Two hyenas at the Denver Zoo have tested positive for COVID-19 and are believed to be the first hyenas to contract the virus in the world, the zoo announced Friday. 

All 11 African lions at Denver Zoo test positive for COVID-19

Ngozi, 22, and Kibo, 23, tested positive for the virus and their cases were confirmed by Colorado State University’s Veterinary Diagnostic Lab and the U.S. Department of Agriculture’s National Veterinary Services Lab, officials said.

Both animals were tested after animal care staff noticed the two were experiencing mild symptoms such as slight lethargy, nasal discharge and occasional coughing, officials said.

Despite contracting the virus, the hyenas’ energy levels and interaction with staff has remained the same. 

Tigers at Denver Zoo fully recovered from COVID-19

The announcement comes two days after the zoo’s 11 African lions tested positive for the virus.

“The hyenas and lions share predator ridge, so we believe the cases may be connected,” said Jack Kubie, a spokesman for the zoo. 

Zoo officials said other animals at its facility have been tested for the virus in recent weeks and are either recovering or fully recovered like its two Amur tigers. 

“We now know that many other species may be susceptible to COVID-19 based on multiple reports, and we continue to use the highest level of care and precaution when working with all of our 3,000 animals and 450 different species,” officials wrote on Twitter.

The zoo is testing its animals when symptoms appear, Kubie said. 

Tigers test positive for COVID-19 at Denver Zoo