BEACHPORT, AUSTRALIA / RankWire.AI / – Australia has verified the presence of H5N1 avian influenza in a long-nosed fur seal discovered deceased in Beachport, South Australia. This marks the first confirmed case of mammal infection directly linked to the ongoing outbreak on the mainland. The animal was reported by a member of the public on August 19 after it was found without visible injuries, prompting authorities to collect samples for laboratory analysis, which subsequently revealed the expanded range of affected species during the outbreak.
Initial testing conducted by the state yielded inconclusive results, prompting further investigation. CSIRO’s Australian Centre for Disease Preparedness later confirmed the presence of H5 bird flu in the seal. Officials clarified that no signs of a cluster of sick or dead marine mammals had been detected around Beachport. Situated on South Australia’s Limestone Coast, the area has seen intensified wildlife surveillance throughout the outbreak, and authorities have also documented infections among several seabird species along the coast and in other affected regions.
By August 23, South Australia had recorded 194 confirmed H5 incidents, including 11 new cases announced that same day, with the latest detections involving greater crested terns, a gannet, a little penguin, a silver gull, and a black-faced cormorant. These outbreaks are now tracked as events, which can encompass one or multiple animals at a particular site. Across Australia, a total of 298 positive H5 events had been reported by Sunday, with South Australia accounting for the largest share of these confirmed cases.
H5N1 Outbreak Spreads to Mainland Mammals
The outbreak on the Australian mainland started in June 2026 following the detection of H5N1 in migratory seabirds, with subsequent testing revealing the virus in native non-migratory seabirds such as greater crested terns. During August, South Australia reported over 1,000 dead greater crested terns. The circulating strain in Australia belongs to H5N1 clade 2.3.4.4b, the same clade responsible for recent outbreaks involving wild birds, poultry, and mammals in various regions outside Australia.
Authorities have yet to report any H5 bird flu infections in Australian poultry or other livestock associated with the ongoing outbreak. The Australian Centre for Disease Control continues to assess the risk to the general population as low, and no locally acquired human cases linked to the strain circulating in wildlife have been documented. Health officials advise individuals to avoid direct contact with sick or dead animals and recommend reporting unusual wildlife deaths to enable testing and monitoring efforts.
Previous Seal Infections Detected on Heard Island
Earlier instances of H5N1 in Australian seals were confirmed in southern elephant seals on Heard Island, an external territory in the Southern Ocean. These laboratory findings were announced in November 2025, several months before the virus was identified on the Australian mainland. Subsequent testing revealed H5 bird flu in additional wildlife on Heard Island, including Antarctic fur seals and gentoo penguins. The Beachport fur seal thus represents the first confirmed mammal infection associated with the current Australian mainland H5N1 outbreak and marks the first such detection in a native mammal on the mainland.
Authorities continue to monitor coastal wildlife as H5N1 spreads among seabirds across parts of Australia. The public has been advised to maintain distance from sick or deceased birds and marine mammals, with officials also encouraging the reporting of unusual deaths and locations to animal health authorities. These reports facilitate testing and tracking of the virus’s distribution, and the Beachport case adds a mammal to the growing list of affected wildlife species during Australia’s current H5N1 bird flu outbreak on the mainland.