H5 Bird Flu in Western Australia: Why Australia’s First Suspected Mainland Case Matters

Australia is facing a potentially defining biosecurity moment after a sick migratory seabird found in southern Western Australia returned a suspected positive result for avian influenza. If further testing confirms the H5 strain, the case would mark the first detection of H5 bird flu on mainland Australia — a development scientists and authorities had long warned was possible as the virus continued its global spread.

The suspected case involves a brown skua, a sub-Antarctic migratory bird, found at Cape Le Grand National Park near Esperance, about 700 kilometres south-east of Perth. The bird was discovered unwell on Sunday, isolated, and later died. Preliminary testing by Western Australian authorities returned a positive result for avian influenza, with samples sent to the CSIRO Australian Centre for Disease Preparedness in Geelong to determine the strain.

The discovery has intensified concern because H5 bird flu has caused devastating wildlife losses around the world, including mass deaths among seabirds, penguins, seals and sea lions. Australia’s mainland has, until now, remained one of the last places without a confirmed case of the deadly H5 strain.

Federal Agriculture Minister Julie Collins stressed that the suspected detection remains limited to a single wild bird and that there is no evidence so far of broader spread.

“If it is confirmed to be the H5 bird flu, this will be sobering, but not unexpected given the spread globally,” Collins said.

A Suspected Case on a Remote WA Beach

The brown skua was found at Cape Le Grand National Park, a remote coastal area near Esperance in southern Western Australia. WA Agriculture and Food Minister Jackie Jarvis said the bird had been isolated after it was found in an unwell state on Sunday and died that night.

Preliminary testing by state authorities returned a positive result for avian influenza on Thursday. Samples were then sent overnight to the CSIRO Australian Centre for Disease Preparedness for further analysis.

“A sick Giant Petrel was also found in the same area and, due to it also being a sub-Antarctic bird, this has also been tested, and we are awaiting results,” Jarvis said.

The involvement of sub-Antarctic bird species is significant. These birds move across remote oceanic environments where H5 bird flu has already been detected, including on Heard Island and McDonald Islands — Australian external territories located about 4,000 kilometres southwest of mainland Australia.

Authorities have not confirmed whether the brown skua came from Heard Island, but its sub-Antarctic range has made the case a focus of urgent biosecurity attention.

Why H5 Bird Flu Is Different

Avian influenza is a virus that mainly affects birds, but some strains can spread to mammals and, rarely, humans. The H5 strain has drawn global concern because of its unusually severe impact on wildlife and its ability to cause mass mortality events across species.

The highly pathogenic H5 strain began causing major seabird mortality outbreaks in the northern hemisphere in late 2021. Since then, it has spread widely through migratory birds and affected wildlife populations across multiple continents.

The virus has been detected in domestic pets such as cats and dogs, farm animals, dolphins, foxes and polar bears. It has also devastated colonies of seals and sea lions, raising concerns about its increasing ability to infect mammals.

For Australia, the suspected Western Australia case matters because the mainland had remained free of confirmed H5 detection despite the strain’s global reach. If confirmed, the virus would have reached the last continent without a confirmed mainland case.

No Evidence Yet of Poultry Infection

Despite the seriousness of the suspected detection, officials have repeatedly emphasized that there is currently no evidence of infection in poultry.

“There is no evidence of any mass mortality at this time, nor is there any evidence of infection in poultry,” Collins said.

That distinction is important for both public reassurance and agricultural planning. A wild-bird detection would trigger increased surveillance and response measures, but it does not automatically mean the virus has entered commercial poultry farms or the broader agricultural system.

“I reiterate that it’s not in the poultry system nor is it in the agriculture system, this is a wild migratory bird and one,” Collins said.

Still, the poultry sector and wider agricultural industry are watching closely. A confirmed H5 case on mainland Australia would create pressure for rapid monitoring, stronger farm biosecurity and coordinated communication between federal, state and territory agencies.

Opposition agriculture spokesman Darren Chester said the case must be investigated thoroughly to protect the poultry industry, the broader agricultural sector and export markets.

“The coalition supports a swift and co-ordinated response by state and federal authorities, working closely with industry and biosecurity agencies,” he said.

The Heard Island Warning

The suspected WA detection follows a devastating outbreak on Heard Island and McDonald Islands, remote Australian external territories in the sub-Antarctic.

The H5 strain was detected there in October, marking the first detection on Australian soil. The islands had long been isolated sanctuaries for breeding birds and marine mammals, but recent surveys showed catastrophic losses.

Drone surveys conducted by the Australian Antarctic Program in October and January found “sobering” images of seal pup carcasses across the grey volcanic shores of Heard and McDonald Islands.

Scientists estimated that 13,359 southern elephant seal pups had died from the disease out of a total population of 17,364. The southern elephant seal pup mortality rate was estimated at 76% across the islands, with one area recording a concentrated death rate of 97%.

“The thing we don’t know from our surveys so far is what the impact was on the breeding adult population of southern elephant seals,” senior research scientist Jarrod Hodgson said.

The scale of the deaths has alarmed wildlife experts because southern elephant seal pup mortality at that level can have lasting effects on future breeding populations. The January data also revealed several hundred adult king penguins had died across Heard Island, with scientists noting mortality above normal levels.

“These observations of H5 bird flu at Heard Island and McDonald Island are the first detection in an Australian external territory and show the continued eastward movement of the virus around the sub-Antarctic,” wildlife biologist Julie McInnes said.

“Our results show a similar pattern to other sub-Antarctic islands, such as South Georgia, where elephant seals have been hardest hit,” added McInnes, who is also lead author of the group’s study.

How the Virus May Have Reached Australian Territory

Genetic analysis suggested the H5 bird flu was likely introduced to Heard Island and McDonald Islands through wildlife from the French sub-Antarctic Crozet Islands, about 1,800 kilometres away. Scientists believe it likely arrived around August 2025.

That finding highlights the central challenge of managing bird flu in remote ecosystems: the virus can move through wild animals across huge distances, often before humans detect it.

Remote islands once viewed as isolated refuges are no longer immune to the spread of highly pathogenic avian influenza. Migratory birds and marine mammals can connect ecosystems separated by thousands of kilometres, carrying pathogens through routes that are difficult to monitor in real time.

The possible Western Australia case brings that concern closer to the mainland.

What the Public Should Do

Authorities are urging people not to touch sick or dead birds or other animals. This advice applies especially in coastal areas where migratory seabirds may be found.

“If you see multiple sick or dead birds or other animals. Please take photos or record it from a safe distance,” Collins said.

“Record your location and go to birdflu.gov.au to report it.”

For people who do not work directly with birds, the risk of catching bird flu in Australia remains low. However, anyone who believes they may have been in contact with infected birds and develops symptoms should speak with a health professional.

Signs of bird flu in birds may include sudden death, lethargy, reluctance to walk, eat or drink, a droopy appearance, ruffled feathers, swelling of the head or limbs, bruising of the wattle, comb, feet or skin, respiratory signs such as panting, nasal discharge or sneezing, diarrhoea, unusual head or neck posture, incoordination, inability to walk or stand, and unusual reduction in egg production.

The key public message is simple: do not handle sick or dead wildlife, keep distance, document the location, and report it.

A Test of Australia’s Preparedness

Australia has been preparing for the possible arrival of H5 bird flu for years. The suspected WA detection is now being treated as a test of that preparedness.

Western Australia is expected to coordinate the immediate response if the case is confirmed, while national coordination would be led by the Department of Agriculture, Fisheries and Forestry. State and territory representatives and industry experts were meeting on Friday afternoon to discuss planning.

“This is a single bird, a suspected case and we are as prepared as any country can be,” Collins said.

“We have invested early, as we said we would, and those investments are now showing provision … if this is detected as a case, we will have gotten there early.”

WA Agriculture and Food Minister Jackie Jarvis said preparations were in place for a “rapid and coordinated national response” to protect poultry producers and manage impacts on wildlife.

Biosecurity planning is likely to focus on surveillance, testing, reporting, wildlife monitoring and communication with poultry producers. If the H5 strain is confirmed, authorities may also increase monitoring across other states and territories.

Wildlife Experts Fear Catastrophic Impacts

While poultry and agriculture are major concerns, wildlife experts are particularly worried about native species.

The Invasive Species Council said the development was deeply concerning, given the devastating global impacts of H5N1 on wildlife.

“If H5N1 is confirmed, the government’s own risk assessment predicts potentially catastrophic impacts on native birds,” policy director Carol Booth said.

“The virus’s increasing ability to infect mammals (also) raises the prospect of severe impacts on marine mammals and other wildlife.”

Carol Booth also described the possible mainland arrival as a serious warning.

“We desperately hope this is not the realisation of our worst dreams,” Dr Booth said.

“The recently reported mass deaths of elephant seals on Heard Island were a harbinger of the potential catastrophe for Australian wildlife if the virus has made it to mainland Australia.”

Even if the suspected case turns out not to be H5N1, experts say it reinforces the need for readiness. Wildlife surveillance, biosecurity protocols and clear reporting systems will be crucial if Australia is to limit the impact of any confirmed outbreak.

Farmers and Industry Watch Closely

The agricultural sector is also bracing for uncertainty. A confirmed H5 detection would not necessarily mean immediate farm losses, but it would raise concern across poultry and livestock industries because of the possible economic and trade implications.

National Farmers Federation chief executive officer Michael Guerin said confirmation would be stressful for farmers and communities.

“Cross-species risk means all livestock sectors need to be prepared, and it reinforces why strong biodiversity is critical for Australia,” he said.

“The economic impact is very hard to gauge. We don’t know where it will impact, what the impact will be, and indeed if it can be contained where it is.

“We’re in the hands of the scientists waiting for confirmation as a first step, and then secondly to be guided by the experience of what comes next.”

For poultry producers, the immediate priority will be prevention. Strong farm biosecurity, rapid reporting of unusual bird deaths and clear guidance from government agencies will be essential if the suspected case is confirmed.

Why the WA Case Has Global Significance

The suspected bird flu detection in Western Australia is not just a local wildlife issue. It is part of a wider global story about how highly pathogenic avian influenza has moved through ecosystems with remarkable speed and severity.

In Argentina in 2022, an outbreak left 96% of southern elephant seal pups dead. Ongoing impacts were still apparent a year later, when only one third of seals returned to breed.

The virus was confirmed in Antarctica in mid 2025 and killed tens of thousands of penguins, seals and sea lions. It was later detected on Heard Island and McDonald Islands in October, followed by the report that more than 13,000 baby seals had died there.

The suspected case in WA may represent the next stage in that eastward movement through sub-Antarctic and migratory pathways.

What Happens Next

The immediate next step is laboratory confirmation from CSIRO’s Australian Centre for Disease Preparedness. Those results are expected to determine whether the virus is the H5 strain of concern and whether it is H5N1.

If confirmed, authorities are likely to expand surveillance, particularly around the discovery site and potentially in other areas used by migratory birds. Wildlife carers, veterinarians, poultry producers, farmers and local communities will likely receive further guidance on reporting and biosecurity.

Officials will also continue monitoring the second sick bird found in the same area — the giant petrel — because it may provide further evidence about whether the virus is present in local or migratory wildlife.

For now, authorities are trying to balance vigilance with reassurance. There is no evidence of poultry infection, no evidence of mass mortality on the mainland, and the suspected case involves a single wild bird.

But the global record of H5 bird flu shows why the case cannot be treated casually.

Conclusion: A Sobering Warning for Australia

The suspected H5 bird flu case in Western Australia is a pivotal moment for Australia’s biosecurity, wildlife conservation and agricultural preparedness.

If confirmed, it would mark the first known detection of the H5 strain on mainland Australia, ending the country’s status as the last continent without a confirmed mainland case. The discovery comes after devastating losses on Heard Island and McDonald Islands, where more than 13,000 southern elephant seal pups are believed to have died.

The immediate risk to most people remains low, and there is no evidence that the virus has entered poultry or agriculture. But the suspected detection is a warning that Australia’s isolation cannot fully shield it from a virus moving through migratory wildlife and remote ecosystems.

The coming test results will determine the next phase of the response. Whether this becomes a confirmed mainland outbreak or remains a suspected single-bird case, the message from authorities and scientists is already clear: Australia must stay alert, act early and treat H5 bird flu as a serious threat to wildlife, farming and national biosecurity.