Thirteen gorillas at a zoo in Georgia have tested positive for Covid-19, officials have said.
It is believed the animals caught the virus from a zookeeper, who was asymptomatic and was wearing personal protective equipment when she went to work.
Staff at Atlanta Zoo became alerted when they noticed the gorillas began showing symptoms such as coughing, nasal discharge and minor changes in appetite.
After tests were carried out, officials confirmed the animals had contracted the virus.
A statement posted to the zoo's website says staff are taking care of the animals and are ready to offer them further support if needed.
One of the gorillas who tested positive for Covid is Ozzie, a male gorilla who celebrated his 60th birthday in June.
Officials are paying attention to Ozzie as the gorilla is thought to be most at risk of Covid complications.
The zoo's statement added that the gorillas live in close proximity to each other in four groups, meaning it is impossible to isolate them individually.
Once the gorillas recover, they will also receive the Zoetis coronavirus vaccine, a jab developed for veterinary use in North America.
The zoo will also vaccinate its Bornean and Sumatran orangutans, Sumatran tigers, African lions, and clouded leopard, the statement said.
Sam Rivera, DVM, Senior Director of Animal Health, said: "The teams are very closely monitoring the affected gorillas and are hopeful they will make a complete recovery.
"They are receiving the best possible care, and we are prepared to provide additional supportive care should it become necessary.
"We are very concerned that these infections occurred, especially given that our safety protocols when working with great apes and other susceptible animal species are, and throughout the pandemic have been, extremely rigorous."
In January, eight gorillas at San Diego Zoo Safari Park contracted Covid-19 but none of them appeared severely ill.
In February, the zoo announced all the animals, including 49-year-old male Winston, had made a full recovery.
In July, a snow leopard at San Diego Zoo also tested positive for Covid after developing a cough and runny nose.
