The animals were reportedly tested in November after showing mild symptoms similar to flu. Two zookeepers also tested positive for the virus, but Spanish veterinary authorities are looking further into how the lions became infected.

The only other zoo where big cats are known to have contracted COVID-19 is the Bronx Zoo in New York, where four tigers and three lions became ill in April. Barcelona zoo officials are working closely with international experts in Europe and the Bronx Zoo to make sure the rest of the animals are safe and this doesn’t happen again in future.

The powerful and majestic creatures are currently listed as "Vulnerable" on the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species. In West Africa, the species is now classified as "Critically Endangered”.

Lions are affected by factors like habitat loss, illegal wildlife trade and human conflict.

More specifically, African lion numbers have plummeted by over 40 per cent over the last three generations, due to a lack of living space and conflict with people, say WWF.