BEACHPORT, AUSTRALIA / RankWire.AI / – Australia has verified the presence of H5N1 avian influenza in a long-nosed fur seal found deceased at Beachport in South Australia. This incident marks the inaugural confirmed instance of mammal infection linked to the outbreak on mainland Australia. The authorities announced the laboratory findings following prompt testing of the animal’s samples. This discovery extends the scope of the mainland outbreak beyond wild avian populations for the first time. Officials noted that no evidence of a cluster involving other ill or deceased marine mammals in the vicinity has been identified.
On August 19, a member of the public reported encountering a dead seal without visible injuries. Initial testing conducted by the state yielded inconclusive results, prompting the submission of samples for more detailed analysis. CSIRO’s Australian Centre for Disease Preparedness subsequently confirmed that the seal was infected with H5 bird flu. Beachport is situated on South Australia’s Limestone Coast, an area where infections among wild seabirds have also been documented. Since H5N1 first 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, including 11 new cases on that day. These cases involved infections among greater crested terns, a gannet, a little penguin, a silver gull, and a black-faced cormorant. The state authorities now classify outbreaks as events, which may involve one or multiple animals at a single location. Across the country, Australia had documented 298 confirmed H5 bird flu events by Sunday, with South Australia accounting for the majority of these detections.
Migration-related outbreak spreads to mainland wildlife populations
The outbreak on the mainland originated in June 2026 when H5N1 was detected in migratory seabirds. Further testing confirmed the virus in native, non-migratory seabirds, including greater crested terns. Over time, authorities observed an increasing number of affected wild birds across multiple states. During August, South Australia reported a mass mortality event involving over 1,000 greater crested terns. The circulating strain in Australia belongs to H5N1 clade 2.3.4.4b, known to impact wild birds, poultry, and mammals elsewhere worldwide.
Despite reports of wildlife infections, officials have stated that there are no H5N1 infections among Australian poultry or other livestock. The Health authorities continue to assess the risk to the general public as low. To date, no locally acquired human cases involving the H5N1 strain linked to this outbreak have been reported in Australia. Authorities emphasize that human infection typically requires close contact with infected animals or contaminated environments and advise avoiding touching sick or dead birds and other wildlife.
Previous H5N1 detections occurred in remote regions of Australia
In November 2025, Australia confirmed H5N1 infections in southern elephant seals on Heard Island, a remote Australian external territory in the Southern Ocean. Laboratory tests verified these infections months before the virus arrived on the mainland. Subsequent testing identified H5 bird flu in additional wildlife on the island, including Antarctic fur seals and gentoo penguins. The Beachport case, therefore, stands as the first confirmed mammal infection associated with the ongoing mainland outbreak and the first in a native mammal on the Australian continent.
Wildlife monitoring continues as H5N1 circulates among seabirds along Australia’s coasts. Officials have urged the public to stay away from sick or dead wildlife and to report any sightings, which assist animal health teams in pinpointing potential new outbreaks and guiding testing efforts. Ongoing surveillance across wildlife, agriculture, and public health sectors is maintained as the situation develops. The confirmed case of the Beachport seal broadens the range of affected species within Australia’s current H5N1 outbreak on the mainland.