Novel rabies outbreak in a marine mammal - the Cape fur seal

Rabies is the oldest documented fatal zoonotic disease, spread between mammals through infected saliva. Outbreaks have only been documented for terrestrial species, with disease risk for marine mammals rarely considered. In June 2024, rabies was confirmed in a marine top predator, the Cape fur seal (CFS, Arctocephalus pusillus pusillus ). We provide the context and timeline of rabies detection following mounting reports of seal aggression, whereby inter-species (seal to domestic dog) transmission prompted diagnostic testing of CFS in South Africa. Laboratory-confirmed cases (n = 94) conservatively date the outbreak in CFS to August 2022; rabies has since been declared endemic to CFS. Aberrant behaviour, hyper-aggression, elevated injury prevalence and confirmation of in-utero transplacental infection were found in this wide ranging, amphibious, highly gregarious and abundant species. Spatio-temporal overlap with vagrant sub-Antarctic pinnipeds makes spillover to other marine mammals possible, creating a subsequent gateway for rabies transmission to Subantarctic Islands and Antarctica, currently rabies-free. At least 135 people have been bitten by suspected or confirmed rabid seals, most receiving post-exposure prophylaxis. Rabies detection in CFS increased between 2022 and 2025 in both diagnostic and systematic surveillance sampling. This suggests an outbreak which is still in an active expansion phase. Considering the tri-partite alliance (FAO-WOAH-WHO) target of zero dog-mediated rabies by 2030, the increasing number of seal attacks towards dogs, and humans raise urgent considerations that should be addressed under One Health.