Introduction to the H5N1 Bird Flu Outbreak in Australia
The deadly H5N1 strain of bird flu has been detected in seabirds across two Australian states. This virus, despite its name, is not limited to birds—it can rapidly infect a variety of animals. In the northern hemisphere, it has caused significant damage to poultry farms and backyard chicken flocks. Additionally, it has been known to infect and even kill cats.
For domestic pet owners, especially those who keep backyard chicken flocks, this development is a cause for concern. It’s essential to be aware of the signs of this highly infectious virus and to think about how you will respond if an outbreak occurs in your area.
Evolution of the H5N1 Virus
Since 2004, I have been studying the H5N1 virus. Over more than two decades, it has evolved into a highly infectious zoonotic disease—capable of jumping between multiple animal species and occasionally affecting humans. The tipping point came in the United States during the 2023–24 period when the virus spread from wild birds to poultry farms and high-density dairy farms in Texas, Kansas, Michigan, and Idaho.
Transmission has also occurred between cattle and cats, with some cats dying after consuming infected cow colostrum (the first milk after a mammal gives birth). In the past three years, cases have been reported in Peru, Chile, and southern Antarctica, including the deaths of thousands of seal pups on Heard Island.
Arrival of the Virus in Australia
Initially, Australian authorities were worried that the virus would arrive from the north during the annual migration of migratory shorebirds. There was uncertainty about whether sick birds would have the strength to fly from far-off Antarctica. However, two of the sick birds found in Western Australia and South Australia were still alive. Given that the virus was first identified on June 20, it’s possible it arrived in Australia much earlier, as these species typically migrate from the sub-Antarctic region starting in March.
The timing makes sense, as the virus is most easily transmitted during cold weather. In China, we saw it emerge around Chinese New Year—a time when low temperatures coincide with high demand for poultry for celebratory meals.
Spread of the Virus from Wild Birds
The World Organisation for Animal Health tracks where the virus is reported for different countries through its WAHIS database. By analyzing this data, we find that it takes between 2 and 6 weeks, on average, for the virus to move into poultry species following the first report in wild birds. Of course, this varies depending on the comprehensiveness of a country’s surveillance and the level of data aggregation provided by different countries reporting to the system.
For example, considering data reported between 2020 and 2024 in Denmark, it took a little more than three weeks between finding the virus in wild birds and reporting it in poultry. In Australia, and considering data from other countries, it is possible we will see outbreaks in poultry in the next 4–5 weeks. This obviously depends on the role bridging species will play in bringing infection into Australian poultry facilities, as well as the level of biosecurity of Australian poultry husbandry systems. Everyone is on high alert, and state and federal agriculture departments have ramped up surveillance and public messaging for producers and the public.
Surveillance and Testing
In the past few years, an avian influenza surveillance system has tested the faeces of wild birds at nesting sites to watch for the virus. Now this surveillance is likely to be expanded to include poultry. Testing will also be informed by farmers, producers, and backyard chicken owners reporting suspected illness.
Risks to Household Pets
Poultry
The risks are very real. When this virus ends up in a densely housed commercial farm, mortality rates of close to 100% are likely. The greatest risk of exposure is when free-range hens spend some time outdoors and are exposed to contact with wild birds. This is the same for backyard chickens.
If you have a flock of chickens, keep them housed as much as possible. “Bridging species” like crows, magpies, and other urban birds can bring infection into backyard flocks. Keep an eye on your chooks and monitor their health for lethargy and neurological signs. If you notice a bird seems disoriented or unwell, you should call the Emergency Animal Disease Hotline on 1800 675 888.
If warranted, a biosecurity officer will come and take nasal swabs and bird droppings away to be tested. In the meantime, you will be asked not to move your poultry and to keep them housed. Unfortunately, all poultry in a farm or backyard flock where H5N1 infection is identified will have to be euthanised.
This virus can infect humans, though it is rare. Do not approach the bird or animal, just call the hotline on 1800 675 888. If there is a need to move the animal, wear gloves and a PPE mask, and dispose of them carefully afterwards.
Cats
Evidence from the US suggests cats are at much greater risk of severe disease than dogs. Where cats ingested contaminated material, such as milk from cattle, there were fatalities. Australian cat owners should be vigilant about what their cat is “investigating” outside, including dead birds.
Dogs
The evidence for serious illness is not as strong as cats. We know they can be exposed, but they don’t seem to be an at-risk species. Other terrestrial carnivores, such as skunks and foxes, have shown neurological illness and respiratory distress. We will have to watch the dingo population closely, because they scavenge on dead wild birds.
Caged Birds
Caged birds such as budgerigars are unlikely to come into contact with wild birds. But if this is possible, and there are signs of illness, these should be reported.
Emergency Contact Information
Emergency Animal Disease Hotline – 1800 675 888
