BEACHPORT, AUSTRALIA / RankWire.AI / – Australia has verified the presence of H5N1 bird flu in a long-nosed fur seal found deceased at Beachport in South Australia. This instance marks the inaugural confirmed infection in a mammal connected to the outbreak on mainland Australia. The authorities announced the laboratory findings after conducting urgent testing on samples from the animal. The discovery broadens the scope of the mainland outbreak beyond wild birds for the first time. Officials also indicated that they found no evidence of a cluster involving other ill or deceased marine mammals nearby.
A member of the public reported the dead seal on August 19, noting it showed no visible injuries. Initial testing by the state yielded inconclusive results, prompting further sample analysis. CSIRO’s Australian Centre for Disease Preparedness subsequently confirmed H5 bird flu in the seal. Beachport is located on South Australia’s Limestone Coast, an area where infections among wild seabirds have already been recorded. Since H5N1 reached mainland Australia earlier this year, the region has become one of several coastal locations affected by the virus.
By August 23, South Australia had documented 194 confirmed H5 bird flu incidents, including 11 new cases that day. These outbreaks involved a variety of 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 multiple animals at a single site. As of Sunday, Australia had recorded a total of 298 positive H5N1 bird flu events nationwide, with South Australia accounting for the majority of reported cases.
Mainland outbreak extends beyond wild avian populations
The outbreak on the mainland started after H5N1 was first detected in migratory seabirds in June 2026. Subsequent testing confirmed the virus in native, non-migratory seabirds, including greater crested terns. Authorities have documented an increase in affected wild bird populations across several states. In August, South Australia experienced mass mortality events involving over 1,000 greater crested terns. The circulating strain in Australia belongs to H5N1 clade 2.3.4.4b, which has impacted wild birds, poultry, and mammals in other regions globally.
Despite the detections in wildlife, no H5N1 infections have been reported in Australian poultry or other livestock. The Health authorities continue to assess the risk to humans as low. There have been no locally acquired human cases involving the H5N1 strain from the current outbreak. Human infections generally require close contact with infected animals or contaminated environments, and officials advise avoiding touching sick or dead birds and wildlife.
Prior H5N1 cases identified in remote territories
Australia previously confirmed H5N1 in southern elephant seals on Heard Island, a remote Australian external territory in the Southern Ocean. Testing confirmed those infections in November 2025, prior to the virus reaching the mainland. Further analysis also detected H5N1 in additional wildlife on the island, including Antarctic fur seals and gentoo penguins. The Beachport case thus represents the first confirmed mammal infection linked to the current mainland outbreak and the first in a native mainland mammal.
Authorities continue surveillance of wildlife as H5N1 circulates among seabirds along various coastal regions. Officials urge the public to stay away from sick or dead wildlife and to record sighting locations. Such reports help animal health teams identify new potential outbreaks and guide testing efforts. Monitoring remains ongoing across wildlife, agriculture, and public health sectors as the outbreak unfolds. The confirmed case in Beachport adds a mammal to the list of species affected by Australia’s mainland H5N1 outbreak.