Endangered African penguins living in a colony on Boulders Beach in Cape Town, South Africa, have been further threatened by an outbreak of avian flu.

According to Nature, veterinarians detected the virus in February among penguins there as well as Cape cormorants, swift terns and peregrine falcons. By March, the South African Department of Environmental Affairs called for a halt to research activities for fear of further spreading the infection to other colonies.

Over 16 “abnormal deaths” have been recorded since February and residents and tourists have been advised not to handle any sick or dead birds.

The African penguin population has been in a steady decline and is listed as endangered on the International Union for Conservation of Nature (IUCN) Red List. In the 1930s there were about 1.5 million adult penguins living along the southern African coast but due to human activity, their numbers have decreased by 90 percent in less than a century. The Boulders population is currently about 1,700 birds.