BEACHPORT, AUSTRALIA / RankWire.AI / – Australia has verified the presence of H5N1 bird flu in a long-nosed fur seal discovered dead at Beachport in South Australia. This instance represents the initial confirmed case of mammal infection associated with the outbreak on the Australian mainland. The authorities revealed the laboratory findings following urgent testing of the animal’s samples. This discovery broadens the scope of the outbreak beyond wild birds for the first time on the mainland. Officials also stated that they had not identified any evidence of a cluster involving other sick or deceased marine mammals in the vicinity.
A member of the public reported the dead seal on August 19 after noticing it showed no visible injuries. The preliminary testing conducted by the state was inconclusive, leading officials to send samples for additional analysis. CSIRO’s Australian Centre for Disease Preparedness later confirmed that the seal was infected with H5 bird flu. Beachport, located on South Australia’s Limestone Coast, is an area where infections among wild seabirds have previously been recorded. The region has become one of several coastal zones affected since H5N1 reached mainland Australia earlier this year.
As of August 23, South Australia had documented 194 confirmed H5 bird flu events, including 11 new cases that day. These events 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 may involve one or multiple animals at a single site. By Sunday, Australia had recorded 298 positive H5 bird flu events nationwide, with South Australia accounting for the majority of those detections.
Spread of the Mainland Outbreak Beyond Wild Birds
The outbreak on the mainland originated after H5N1 appeared in migratory seabirds in June 2026. Subsequent 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 several states. During August, South Australia also experienced mass mortality involving over 1,000 greater crested terns. The virus circulating in Australia is identified as H5N1 clade 2.3.4.4b, a strain known to have impacted wild birds, poultry, and mammals in other parts of the world.
Despite detections in wildlife, authorities have found no evidence of H5N1 infections in Australian poultry or other livestock. The Health authorities continue to assess the risk to the general population as low. To date, no locally acquired human cases involving the H5N1 strain from this outbreak have been reported in Australia. They advise that human infection typically requires close contact with infected animals or contaminated environments and recommend avoiding contact with sick or dead birds and other wildlife.
Previous H5N1 Incidents on Remote Australian Territory
Australia previously confirmed H5N1 in southern elephant seals on Heard Island, a remote external territory in the Southern Ocean. Laboratory tests verified these infections in November 2025, several 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. The case in Beachport is therefore the first confirmed mammal infection associated with the current mainland outbreak, and it marks the first detection in a native mainland mammal.
Wildlife surveillance efforts continue as H5N1 circulates among seabirds along Australia’s coast. Authorities urge the public to stay away from sick or dead wildlife and to record any sightings, which can assist animal health teams in identifying new potential events and guiding testing efforts. Monitoring remains active across wildlife, agriculture, and public health systems as the outbreak unfolds. The confirmed case in the Beachport seal expands the known range of species affected by Australia’s mainland H5N1 outbreak, including mammals.