At the San Diego Zoo Safari Park, several gorillas have tested positive for the coronavirus in what is believed to be the first known cases among such primates in the United States and possibly the world.

Lisa Peterson, the park’s executive director, told The Associated Press on Monday that eight gorillas that live together at the park are believed to have the virus and several have been coughing.

A member of the park’s wildlife care team who also tested positive for the virus but has been asymptomatic and wore a mask at all times around the gorillas, is thought to be the virus source. The park has been closed to the public since Dec. 6 as part of the state of California’s lockdown efforts to curb coronavirus cases.

Other wildlife has contracted the coronavirus from minks to tigers, however, this is the first known instance of transmission to great apes and it is unknown if they will have any serious reaction.

Wildlife experts have expressed concern about the coronavirus infecting gorillas, an endangered species that share 98.4 percent of their DNA with humans and are inherently social animals.