The Global Virus Network (GVN) is closely monitoring detections of highly pathogenic avian influenza A (H5N1), commonly known as bird flu, in several mammal species in Australia as the virus continues to spread among birds and mammals worldwide.
On Sept. 13, Australian authorities confirmed the first detection in an Australian sea lion, an endangered species, at Seal Bay on Kangaroo Island. Australia reported its first confirmed detection in a mammal on Aug. 23, when a long-nosed fur seal found at Beachport in South Australia tested positive. A second long-nosed fur seal near Kangaroo Island was confirmed two days later. Subsequent detections included a red fox in metropolitan Adelaide, a common dolphin at Goolwa and a second fox at Normanville.
The detections show the virus infecting several mammal species in Australia within weeks of its first reported appearance in the country's wildlife. Globally, H5N1 has infected a growing range of mammals, including seals and other marine mammals, dairy cattle, cats and wild carnivores. Scientists are monitoring these infections for changes in the virus and evidence of transmission between mammals.
Australian authorities report no evidence of mammal-to-mammal transmission of the virus in Australia.
"Given what we have seen with this H5N1 genotype in seal and sea lion populations overseas, a spillover into Australian marine mammals was a possibility we had been concerned about and actively monitoring for," said Michelle Wille, Ph.D., an avian influenza researcher affiliated with the University of Melbourne and the WHO Collaborating Centre for Reference and Research on Influenza and the Peter Doherty Institute for Infection and Immunity, a GVN Center of Excellence in Australia. "While it is sobering to see that possibility become a reality, the priority now is detailed genomic analysis of this and any future detections. We need to closely monitor for mutations associated with better adaptation to mammals and determine whether infections represent separate spillover events from birds or evidence of transmission between seals. That distinction will be critical to understanding the risk posed by the virus as it continues to circulate in wildlife."
Australia first detected H5N1 clade 2.3.4.4b in wild seabirds in June. The virus has since been found in wild birds across several parts of the country. As of Sept. 17, Australia had reported 576 confirmed events in wildlife, including mass mortality events in greater crested terns. An event may involve one or more animals.
There have been no detections in Australian poultry or the agricultural production system. The Australian Centre for Disease Control continues to assess the risk to people as low and reports no evidence that the virus circulating in Australia has changed to infect people more easily.
Human H5N1 infections have occurred, most often after contact with infected animals or contaminated environments. The World Health Organization reports no sustained person-to-person transmission.
In April 2025, GVN published an analysis in The Lancet Regional Health – Americas calling for stronger surveillance, biosecurity, genomic monitoring and preparedness as H5N1 spread. In April 2026, GVN issued a statement on H5N1 vaccine developments, emphasizing the need for continued vaccine development and broader pandemic preparedness.
"Australia is another reminder that H5N1 is a global animal health issue with implications for human health that we need to continue watching closely," said Sten H. Vermund, M.D., Ph.D., GVN's chief medical officer and dean of the University of South Florida College of Public Health. "There is no reason for alarm, but there is every reason to remain vigilant. Surveillance across species, rapid genomic analysis and open sharing of what we learn give us the best chance to recognize an important change in the virus early."
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