The two hippos, Harmein, 41, and Imani, 14, have not shown any symptoms other than a runny nose, according to the zoo.
“The hippo building was immediately closed after the first positive test and will remain temporarily closed until Hermien and Imani test negative,” the zoo said in a Facebook statement on Friday.
Covid infections have so far been reported in several animals, including felines like lions and tigers and other mammals including deer.
Felines at several zoos around the world have also died after contracting the infection.
Three snow leopards died at a Nebraska zoo last month after suffering from the disease and two Asiatic lions tested positive died at an Indian zoo in June.
Pets such as cats, dogs and ferrets have also been carriers of the virus after coming into contact with infected humans in some cases. Cases of Covid have also been reported in primates, hyenas and otters.
Although the risk of spreading the virus from animals to humans is low, people could still pass the virus to pets and other animals, according to the United States Centers for Disease Control and Prevention.
But the new report is probably the first case of this type of coronavirus infection in hippos.
“To my knowledge, this is the first known contamination in this species. Globally, this virus has mainly been reported in great apes and felines, ”said zoo veterinarian Francis Vercammen.
Antwerp Zoo said it is currently investigating how the virus has spread to its hippos.
The hippo caregivers have already tested negative for Covid and “none of them have recently contracted the disease,” the zoo statement said.
Jeremy Farrar, director of the Wellcome Trust charitable foundation and one of Britain’s foremost scientific figures, said in a tweet that it is very important to understand the “full range of potential animal reservoirs” for the new coronavirus in the wild as well as in the domesticated animal sector.
A large animal reservoir could mean multiple pathways for the virus to evolve, he explained.