The only other known case of rabies in a sea mammal was in a ringed seal in Norway's Svalbard islands in the early 1980s. That seal had likely been infected by a rabid arctic fox, researchers said, and there was no evidence of rabies spreading among seals there.

Rabies infects mammals and can be passed on to people. The virus is almost always fatal once symptoms appear and it spreads via saliva, usually through bites but also sometimes when animals lick and groom each other.

Officials in South Africa say they are experiencing a rabies outbreak among its wild seal population. It's the first time they say an outbreak of the virus has been found in sea mammals. A representative for the city of Cape Town says it received reports of aggressive seals from local residents,