BEACHPORT, AUSTRALIA / RankWire.AI / – Australia has identified H5N1 avian influenza in a dead long-nosed fur seal discovered at Beachport in South Australia. This finding represents the first verified case of mammal infection linked to the outbreak on mainland Australia. After prompt laboratory testing of the animal’s samples, officials announced the results. This case extends the scope of the outbreak beyond wild birds for the first time on the mainland. Authorities noted that there was no evidence of a cluster involving other sick or deceased marine mammals nearby.
The dead seal was reported by a member of the public on August 19, who found it without any visible injuries. Initial testing at the state level yielded inconclusive results, leading officials to send samples for further analysis. CSIRO’s Australian Centre for Disease Preparedness later confirmed the presence of H5 bird flu in the seal. Beachport is situated on South Australia’s Limestone Coast, an area where infections among wild seabirds have previously been documented. Since H5N1 reached mainland Australia earlier this year, this region has become one of several coastal zones affected by the virus.
By August 23, South Australia had reported a total of 194 confirmed H5 bird flu events, including 11 new cases that day. These cases involved various species such as greater crested terns, a gannet, a little penguin, a silver gull, and a black-faced cormorant. The state now classifies outbreaks as events, which can encompass one or multiple animals at a single location. Across Australia, a total of 298 positive H5N1 bird flu events had been documented by Sunday, with South Australia accounting for the majority of these confirmed detections.
Mainland Australia’s Outbreak Expands Beyond Wild Birds
The outbreak on the mainland began when H5N1 appeared in migratory seabirds in June 2026. Subsequent testing confirmed the virus in native, non-migratory seabirds, including greater crested terns. Authorities observed an increasing number of affected wild birds across multiple states, with South Australia experiencing a significant die-off of over 1,000 greater crested terns during August. The circulating strain in Australia is identified as H5N1 clade 2.3.4.4b, which has impacted wild birds, poultry, and mammals elsewhere globally.
Despite numerous wildlife detections, authorities have reported no cases of H5N1 in Australian poultry or other livestock. The Australian Centre for Disease Control maintains the assessment that the risk to the general public remains low. There have been no locally acquired human cases of H5N1 in Australia to date. Health officials emphasize that human infection typically requires close contact with infected animals or contaminated environments. They advise avoiding touching sick or dead birds and other wildlife.
Previous H5N1 Incidents Reported on Remote Territories
H5N1 has been previously confirmed in southern elephant seals on Heard Island, a remote Australian external territory in the Southern Ocean. Laboratory analysis verified those infections in November 2025, months before the virus was detected on the mainland. Further testing identified H5 bird flu in additional wildlife on the island, including Antarctic fur seals and gentoo penguins. Consequently, the Beachport case marks the first confirmed mammal infection associated with the current mainland outbreak and the first in a native mainland mammal.
Wildlife monitoring persists as H5N1 circulates among seabirds along Australia’s coast. Authorities urge the public to avoid contact with sick or dead wildlife and to report any sightings, helping animal health teams identify potential new cases and direct testing efforts. Ongoing surveillance continues across wildlife, agriculture, and public health sectors as the outbreak unfolds. The confirmed case in Beachport extends the range of affected species, now including mammals, within Australia’s ongoing H5N1 mainland outbreak.