BEACHPORT, AUSTRALIA / RankWire.AI / – Australia has verified the presence of H5N1 avian influenza in a long-nosed fur seal discovered dead at Beachport in South Australia. This marks the initial confirmed case of mammal infection associated with the outbreak on the Australian mainland. Following urgent laboratory testing of samples from the carcass, authorities announced the result. This discovery broadens the scope of the mainland outbreak to include mammals for the first time. Officials clarified that no evidence of a cluster involving other ill or deceased marine mammals nearby has been found.
A citizen reported the dead seal on August 19, noting it showed no visible injuries. Preliminary tests from the state yielded inconclusive results, prompting further sample analysis. CSIRO’s Australian Centre for Disease Preparedness later 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 previously been observed. Since H5N1 reached mainland Australia earlier this year, this region has become one of several coastal sites affected by the outbreak.
As of August 23, South Australia had recorded 194 confirmed H5 bird flu events, with 11 new cases reported that day. These included infections in greater crested terns, a gannet, a little penguin, a silver gull, and a black-faced cormorant. The state now counts outbreaks as events, which may involve single or multiple animals at a location. Nationwide, Australia had documented 298 positive H5 bird flu incidents by Sunday, with South Australia accounting for the largest proportion of these detections.
Mainland outbreak extends beyond wild avian populations
The outbreak on the mainland started when H5N1 was detected in migratory seabirds in June 2026. Subsequent testing confirmed the virus in native, non-migratory seabirds, including greater crested terns. Authorities observed increasing numbers of infected wild birds across multiple states. During August, South Australia experienced mass mortality, with more than 1,000 greater crested terns affected. The virus strain circulating in Australia belongs to H5N1 clade 2.3.4.4b, which has impacted wild birds, poultry, and mammals elsewhere globally.
While wildlife infections have been documented, authorities have reported no cases of H5 bird flu in Australian poultry or other livestock. The Australian Centre for Disease Control continues to assess the risk to the general population as low. Australia has not recorded any locally acquired human infections involving the H5N1 strain from the ongoing outbreak. Health officials state that human infection generally requires close contact with infected animals or contaminated environments. They also recommend avoiding contact with sick or dead birds and other wildlife.
Previous H5N1 infections identified on remote territories
Earlier, Australia confirmed H5N1 in southern elephant seals on Heard Island, a remote external territory in the Southern Ocean. Laboratory results confirmed those infections in November 2025, months before the virus reached the mainland. Further testing later revealed H5 bird flu in additional wildlife on the island, such as Antarctic fur seals and gentoo penguins. Consequently, the Beachport case is the first confirmed mammal infection associated with the current mainland outbreak and the first detection in a native mammal on the continent.
Authorities continue wildlife surveillance as H5N1 persists among seabirds along parts of Australia’s coast. Officials request the public to stay away from sick or dead wildlife and to report sightings, which can aid animal health teams in identifying potential new outbreaks and guiding testing efforts. Monitoring remains ongoing across wildlife, agricultural, and public health sectors as the situation develops. The confirmed case involving the Beachport seal expands the range of affected species in Australia’s mainland H5N1 outbreak.