BEACHPORT, AUSTRALIA / RankWire.AI / – Australia has officially identified H5N1 avian influenza in a long-nosed fur seal discovered dead at Beachport in South Australia. This marks the first time that a mammal infection has been confirmed in connection with the outbreak on mainland Australia. The authorities announced the results after conducting urgent tests on samples taken from the deceased animal. This discovery extends the scope of the mainland outbreak beyond wild birds for the very first time. Officials stated that they found no signs of a cluster involving other ill or deceased marine mammals nearby.
A member of the public reported finding the dead seal on August 19, noting it showed no visible injuries. Initial testing conducted by the state returned inconclusive results, prompting officials to send samples for more detailed analysis. CSIRO’s Australian Centre for Disease Preparedness subsequently confirmed the presence of H5 bird flu in the seal. Beachport is located on South Australia’s Limestone Coast, an area where authorities have documented infections among wild seabirds. Since H5N1 reached mainland Australia earlier this year, the region has become one of several coastal zones affected by the outbreak.
By August 23, South Australia had reported 194 confirmed H5 bird flu cases, including 11 new instances that day. These cases involved greater crested terns, a gannet, a little penguin, a silver gull, and a black-faced cormorant. The state now categorizes outbreaks as events, which may involve multiple animals at a single location. Overall, Australia had recorded 298 positive H5 bird flu events nationwide by Sunday, with South Australia accounting for the majority of these detections.
Expansion of the mainland outbreak beyond wild avian populations
The outbreak on the mainland started after H5N1 was detected in migratory seabirds in June 2026. Subsequent testing confirmed the virus in native, non-migratory seabirds such as greater crested terns. As a result, authorities documented an increasing number of affected wild birds across several states. During August, South Australia also experienced mass mortality events involving more than 1,000 greater crested terns. The circulating virus in Australia belongs to H5N1 clade 2.3.4.4b, which has impacted wild birds, poultry, and mammals in various parts of the world.
Despite these wildlife detections, officials have reported no cases of H5 bird flu in Australian poultry or other livestock. The Health authorities maintain that the risk to humans remains low. So far, Australia has not recorded any locally acquired human cases involving the H5N1 strain from the current outbreak. Human infections generally require close contact with infected animals or contaminated environments, according to health officials. They advise avoiding contact with sick or dead birds and other wildlife to reduce any risk.
Previous H5N1 cases identified in remote Australian territories
H5N1 was previously confirmed in southern elephant seals on Heard Island, an isolated Australian external territory in the Southern Ocean. Laboratory tests verified those infections in November 2025, months before the virus appeared on the mainland. Further testing later detected H5 bird flu in additional wildlife on the island, including Antarctic fur seals and gentoo penguins. Therefore, the Beachport case represents the first confirmed mammal infection linked to the current mainland outbreak. It is also the first detection in a native mainland mammal.
Authorities continue to monitor wildlife as H5N1 circulates among seabirds along Australia’s coast. They have asked the public to stay away from sick or dead wildlife and to record sightings’ locations. These reports help animal health teams identify potential new cases and guide testing efforts in affected regions. Monitoring remains active across wildlife, agriculture, and public health sectors as the outbreak unfolds. The confirmation of the Beachport seal case expands the range of affected species, including mammals, within Australia’s ongoing H5N1 mainland outbreak.