Several gorillas and lions at Rotterdam’s Blijdorp Zoo have tested positive for coronavirus, which they may have picked up from an employee without any symptoms, the zoo confirmed on Friday.

The animals are showing flu-like symptoms: they are listless, have less appetite, a slight cough and the gorillas also have stomach and intestinal problems, the zoo said.

Given that the animals are in good health, the zoo said it expected the virus to have a mild effect on them. Research from zoos in the United States and elsewhere has shown the condition of the animal before infection is important for the course of the disease.

The zoo said there is no risk to visitors and the gorilla and lion enclosures were closed after coronavirus was first suspected, so the animals were effectively quarantined.

It is the first time since the outbreak of the corona pandemic that animals at the zoo have tested positive for coronavirus.