BEACHPORT, AUSTRALIA / RankWire.AI / – Australia has officially identified H5N1 avian influenza in a long-nosed fur seal discovered deceased at Beachport in South Australia. This discovery signifies the first confirmed case of mammal infection associated with the outbreak on the Australian mainland. The confirmation came after urgent laboratory testing of samples collected from the animal. This finding extends the scope of the mainland outbreak beyond wild avian populations for the first time. Authorities also stated that investigations have not revealed any evidence of a cluster involving other ill or dead marine mammals in the vicinity.
A member of the public reported the dead seal on August 19, noting it showed no obvious signs of injury. Initial testing by the state yielded inconclusive results, leading officials to send samples for more detailed analysis. CSIRO’s Australian Centre for Disease Preparedness later confirmed the presence of H5 bird flu in the seal. Located on South Australia’s Limestone Coast, Beachport is an area where authorities have previously documented infections among wild seabirds. Since H5N1 reached mainland Australia earlier this year, this region has become one of several coastal sites affected by the virus.
By August 23, South Australia had recorded 194 confirmed H5 bird flu events, with 11 new cases reported that day. These incidents involved various species, including greater crested terns, a gannet, a little penguin, a silver gull, and a black-faced cormorant. The state authorities now categorize outbreaks as events, which may involve single or multiple animals at a given location. Overall, Australia had documented 298 positive H5 bird flu events across the country by Sunday, with South Australia accounting for the majority of these reported cases.
Mainland outbreak extends beyond wild avian populations
The outbreak on the mainland was triggered by the emergence of H5N1 in migratory seabirds in June 2026. Follow-up testing confirmed the virus in native, non-migratory seabirds, including greater crested terns. Authorities observed a rise in affected wild bird populations across several states. In August, South Australia reported the mass death of over 1,000 greater crested terns. The strain circulating in Australia belongs to H5N1 clade 2.3.4.4b, which has impacted wild birds, poultry, and mammals in various regions worldwide.
Despite detections in wildlife, officials have found no signs of H5N1 infections in Australian poultry or other livestock. The Health authorities continue to classify the overall risk to the general population as low. To date, no locally acquired human cases involving the H5N1 strain linked to the current outbreak have been reported in Australia. Human infection generally requires close contact with infected animals or contaminated environments, and authorities recommend avoiding touching sick or dead birds and other wildlife.
Previous H5N1 cases identified in remote regions
Earlier, Australia confirmed H5N1 infections in southern elephant seals on Heard Island, a remote Australian external territory in the Southern Ocean. Laboratory results in November 2025 verified those cases, several months before the virus appeared on the mainland. Additional testing also detected H5 bird flu in other wildlife on the island, including Antarctic fur seals and gentoo penguins. The Beachport incident is therefore the first confirmed mammal infection linked to the ongoing mainland outbreak and marks the first detection in a native mammal on the mainland.
Wildlife surveillance continues as H5N1 persists among seabirds along Australia’s coast. Officials have urged the public to avoid contact with sick or dead wildlife and to report any sightings, aiding animal health teams in identifying new events and guiding testing efforts. Monitoring remains active across wildlife, agriculture, and public health sectors as the outbreak evolves. The confirmed case involving the Beachport seal broadens the range of affected species in Australia’s ongoing H5N1 mainland outbreak.