Rabid seals in South Africa are attacking people in the first known major outbreak of the disease among marine mammals.
Eleven seals have so far tested positive for rabies in Cape Town. The animals are usually playful toward humans, but the outbreak is leading seals to act strangely and aggressively, alarming surfers and beachgoers, experts say.
Rabies is a deadly viral disease primarily transmitted through saliva that affects the central nervous system. Symptoms include fever, pain and tingling, pricking or burning sensations at the wound site, according to the World Health Organization. Unless medical attention is given immediately after exposure, the virus spreads to the central nervous system and leads to fatal inflammation of the brain and spinal cord. Symptoms can take anywhere between a week and two years to appear, but they usually occur one to three months after exposure.
The last recorded case of a seal contracting the disease was in 1980 in Norway's Svalbard islands, The Guardian reported July 11. The new upsurge in cases is thought to be the world's first significant outbreak of rabies in marine mammals, but it's unclear how the disease entered the seal population.
South African fur seals (Arctocephalus pusillus) began behaving strangely a few years ago, Gregg Oelofse, the coastal manager for the City of Cape Town, told The Guardian. A spike in reported seal attacks in late 2021 suggested the animals were acting more aggressively than usual toward humans, he said.
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Together with scientists and animal welfare experts, Oelofse and his team captured and tested a few animals through 2022 to determine the cause of this sudden aggression. But given there was only one previous known case of rabies in seals, the team did not test for the disease, so they were left stumped.
The answer only came earlier this year, when a seal bit at least three surfers in a matter of minutes in the waters off Muizenberg beach, 12 miles (19 kilometers) south of Cape Town's city center. "This little seal came up at me at high speed," one of the surfers said in a video posted on Facebook in May. "It lurched onto my back and bit a hole into my wetsuit over here and kind of bit me on the backside."
The seal then latched onto the man's surfboard and started biting it, the surfer said. "Eventually it let go, but then it kept coming back at me all the time," he said.
Around the same time, a seal was also seen swimming ashore with bloody injuries on its face likely inflicted by another extremely aggressive seal, according to The Guardian. Together with the attack at Muizenberg beach, this prompted authorities to euthanize four seals and test them for rabies.
Tests showed that three of the four seals were infected with rabies, and the number of reported cases has since grown to 11 along Cape Town's 190-mile-long (300 km) coastline, CNN reported July 12.
Despite daily contact between seals and surfers, the disease seems to have remained in the seal population. "We think quite a few people have been bitten by rabid seals, but luckily no human has got infected yet," Oelofse told The Guardian. The reason for this is unknown, he said.
Swimmers and surfers are nevertheless advised to exercise extreme caution and to seek immediate medical attention if a seal bites them.
Surfers used to enjoy interacting with seals, which are curious and playful creatures. "But now everyone was paddling as fast as they could to get away," Oelofse said. While people should avoid seals that are behaving strangely or showing signs of aggression, there is no reason to fear animals that appear relaxed, he added.
Scientists are now sequencing the rabies virus to pinpoint where and when it entered the seal population and to determine how far it has spread. South African fur seals form dense colonies, meaning the disease could become endemic and eventually spread to other mammals, such as African clawless otters (Aonyx capensis), The Guardian reported.
