Going viral

Highly Pathogenic Avian Influenza continues its spread around the globe, reaching Antarctica earlier this year. Australia remains free of the variant—for now. Natasha Harris reports.

As winter wanes, wardens at the Broome Bird Observatory start their lookout for returning migratory shorebirds. Unlike their departure at the end of summer, when they leave in coordinated flocks in the afternoon when conditions are right, their arrival happens in dribs and drabs, at any time of the day—not surprising, given the feat of endurance that is their migration journey. So wardens have their eyes peeled for particular species like the Common Sandpiper. This species is a great indicator for the start of migration as one of the first species to arrive, and because they completely vacate Australia in the winter. Their arrival is a sign that some birds have reached the end of their journey, and the return of our migratory shorebirds has begun.

This year, the excitement is tinged with apprehension. Australia is one of the last places in the world to detect an outbreak of the deadly bird flu variant H5N1 that has ravaged bird populations around the world. Experts agree that it’s only a matter of time, and if it does arrive in Australia through wild birds rather than through a failure of quarantine, it will likely be with the migratory shorebirds . “Being where we are, and watching birds all day, certainly makes our role in vigilance pretty important,” says Matt Hansen, one of our current BBO wardens. “The earlier we detect an incursion, the better our response can be.

Much ado about bird flu

Bird flu is nothing new. As with human influenza viruses, numerous avian flu viruses circulate and evolve each year, carefully tracked by virologists but only occasionally making the news. So-called ‘low pathogenic’ avian influenza—a designation which reflects their impact on poultry—is part of the natural viral community in wild birds, rarely causing disease, and not transmitting easily between birds. Waterbirds, and particularly waterfowl like ducks, geese and swans, are natural reservoirs of avian flu.

When the virus enters industrial poultry farms, the vast numbers of birds in close confines is the perfect environment for explosive rates of viral transmission, and more importantly, mutation. As with human viruses, this kind of viral mutation is a lottery, and occasionally a variant emerges with a ‘winning’ combination of being highly contagious and causing severe disease. Highly pathogenic avian influenza viruses (HPAI), as their name suggests, cause severe illness and death in poultry, and necessitate the ‘depopulation’ of millions of birds to halt the spread. In Australia, we’ve had numerous outbreaks of HPAI, all arising from poultry farms, and resulting in the death of millions of farmed birds . Still, these HPAIs are rarely a problem for wild birds, because they tend to peter out through low transmission and developed immunity, never spreading much beyond waterfowl.

Until now. The variant of HPAI, known as H5N1, is a gamechanger: not only does it cause fatal disease in wild birds as well as poultry and seems to persist throughout the year well into the breeding season, it also spreads readily, both between bird species and into mammals. This viral ‘spillover’ from poultry operations into wild populations of birds is what conservationists dread: hitting wild birds with a pathogen evolved in unnatural conditions that defies their natural immunity. Unlike previous outbreaks of HPAI among wild birds in Europe and North America, which were largely confined to waterfowl, H5N1 has caused deaths in most major bird groups, including parrots, falcons, owls and eagles, along with waterbirds, shorebirds, waders and seabirds, with infections in more than 400 different bird species recorded. And so far, Australia has remained free of this deadly panzootic (the animal equivalent of a pandemic), which gives us a unique opportunity to learn from what has happened overseas.

H5N1 Bird Flu—How you can help

If you see any of the following signs in wild birds, contact the hotline:

• Lack of coordination, tremors
• Twisted neck or abnormal posture
• Difficulty breathing, standing or flying
• Swelling in the neck, head and eyes
• Coughing or sneezing
• Numerous dead birds in one location

Do not touch or approach sick or dead birds.

Record any details about the location and take photos if possible, and report to the Emergency Animal Disease Hotline on 1800 675 888.

For more information read our FAQs and Fact Sheet.

Six degrees of contagion

Since 2020, H5N1 has spread rapidly around the globe. Transmitted through water, faeces and direct contact, the virus has followed the migration pathways of waterbirds, rapidly infecting colonies and causing unprecedented mass mortalities. The first mass death events were reported among waterbirds in 2021: Great Skuas and Barnacle Geese in Scotland, Common Cranes in Israel, Great White Pelicans in Senegal and Caspian and Royal Terns and Grey-headed Gulls along the southern coast of Africa. By 2022, it had hit Northern Gannets in Scotland, causing a 25 per cent decline in the largest breeding colony, and an even greater decline of 60 per cent reported in the same species in Quebec.

Songbirds, for instance, don’t readily contract or spread avian flu, though some individuals in North America and Canada have been detected in this current outbreak. Raptors, on the other hand, appear to be particularly susceptible to the disease, and as scavenging animals, can contract the virus through ingestion of sick birds or animals.

As far as humans are concerned, experts agree that there is little to no chance that H5N1 could cause a pandemic: though some people have contracted this bird flu, all have involved close contact with affected birds or cows.  Humans are regarded by virologists as ‘dead end hosts’: there is little evidence so far to show that humans can pass it on to other humans. As the Federal government confirms: “It is clear that [bird flu] is a virus of birds which on rare occasions infects a human.”

Thanks to our unique geography and the fact that ducks and geese from the northern hemisphere don’t migrate here, Australia is one of the last holdouts, but this may be a double-edged sword. With a population of native birds naive to the virus, when it does hit, the results could well be catastrophic.

Be prepared

Since 2022, BirdLife Australia has been working with Wildlife Health Australia and the Threatened Species Commissioner on the National HPAI Steering Group to prepare for the impact of HPAI on our wild birds. Knowing where it might hit, and what we can do to mitigate the extent of transmission and protect vulnerable populations, is crucial to an effective response to the potential disaster.

One of the vital pieces of preparedness is data: data on bird populations and locations, range dynamics of different bird groups and places where they come together, and which bird groups may be more susceptible, either genetically or behaviourally. With our extensive datasets, collected over many decades by volunteers and staff, BirdLife Australia has helped create public mapping tools that help us better understand the incursion points for the virus, and its spread pathways once it hits our shores. Deakin University’s Marcel Klaassen, who led a decade-long study analysing the species most likely to carry the virus into Australia, has collaborated with us on a national risk-mapping tool for waterbird abundance and movement, drawing on the most significant waterbird, shorebird and seabird datasets in the country.  This information reveals pathways the virus is likely to take and identifies ‘hot spots’ where high densities of notable species occur.

Since 2005, Wildlife Health Australia has managed the targeted surveillance of wild birds for avian influenza, sampling waterbirds where they mix with shorebirds or come into close proximity with humans or poultry. With the advent of H5N1, sampling of shorebird species has increased, with around a thousand samples tested in 2024, taken from the Victorian coast and offshore islands, right up to Exmouth in Western Australia.

Just weeks ago, BirdLife’s Migratory Shorebirds Coordinator Lindall Kidd was in Exmouth Gulf with members of the Australian Wader Studies Group for a tracking study of migratory shorebirds in this region. Since this project began last year, the banding and tracking of Exmouth shorebirds has also involved collecting samples for flu surveillance. With Marcel Klaassen and Doherty Institute’s Dr Michelle Wille––the country’s leading avian influenza experts––in tow, this year they collected 126 samples from nine species. Thankfully, all were negative.

…though some people have contracted this bird flu, all have involved close contact with affected birds or cows.

In the crosshairs

With the coming of H5N1 a veritable certainty, which of Australia’s birds are most susceptible to the virus, and what might an outbreak look like?

While colonial-nesting waterbirds are clearly vulnerable, as the combination of large gatherings and water amount to a ‘super-spreader event’, on the conservation front, other factors come into play. The current status of a species is paramount. For birds like the Orange-bellied Parrot and Regent Honeyeater that have intensive zoo-breeding programs supporting precariously low wild populations, the loss of even a small number of birds would set conservation efforts back by decades and possibly result in functional extinction. Even though passerines—the largest order of birds, comprising all perching and songbirds—are not highly affected by avian flu and don’t spread it easily, the virus has caused deaths in at least 18 passerine species in the USA, including crows, sparrows, ravens and magpies.

Along with population size, factors like range and relative isolation are also important. For birds with isolated populations and poor ability to flee from exposure, or recolonise the area once it has passed, the virus poses a real threat of local extirpations. Should the worst happen and the virus ravages a population, there’s no back-up to save the species. For species with small populations, like the Orange-bellied Parrot and Gould’s Petrel, it could even mean global extinction.

The Christmas Island Frigatebird is another susceptible species. This majestic pirate of the skies is already Endangered, with fewer than 2,000 breeding pairs left, and breeds only on Christmas Island. Late last year, mass mortalities occurred in Great and Magnificent Frigatebirds on the coast of Ecuador due to H5N1, with thousands of birds killed by the virus. The frigatebirds’ distinctive predatory habits—stealing prey from other birds, or forcing them to regurgitate their meals, a process known as kleptoparasitism—make them particularly vulnerable to contracting the virus, either from the bird they have robbed or from the meal itself. In addition, their migration to Java, where HPAI is already endemic. could put them in contact with many other birds, and increases the chances contracting the virus and bringing it back to the island.

Birds with similarly restricted breeding ranges and small populations, like the Abbott’s Booby (Christmas Island) and Gould’s Petrel (three islands off the New South Wales coast) are also species of concern. Again, both boobies and petrels have been affected around the world, with the Peruvian Booby of South America being particularly hard-hit last year, with over 200,000 boobies dead in Chile and Peru.

At Victoria’s Gippsland Lakes, BirdLife Australia’s Deb Sullivan has been working with Australian Pelicans for nearly a decade. Along with coordinating the Great Pelican Count, which sees nearly a hundred volunteers converge on the lakes in autumn for a one-day count, she also coordinates one of four pelican banding studies in Australia, aimed at filling in the knowledge gaps about where and how far pelicans move around between breeding seasons. And now, her work also involves sampling for avian flu.

The devastating accounts of pelican mortalities from around the world are a grim warning for what might be in store for our beloved Australian Pelican: the death of nearly half of Greece’s Dalmatian Pelican population in 2022, including 60 per cent of the largest colony, in a matter of months—Greece’s ‘worst ever wildlife disaster’. Already listed as Near Threatened, the population will take decades to recover, even if no further adverse events take place. And in South America, where the virus hit at the end of 2022, the Peruvian Pelican was decimated. Also listed as Near Threatened by the IUCN, but Endangered in Peru, more than a third of the Peruvian population was dead by the middle of 2023, with further losses in Chile.

The colonial nesting habits of pelicans fuel the spread of the virus, but the extent of the mortality has researchers concluding that pelicans are particularly susceptible genetically to H5N1 as well. Could the same be the case with our pelican?  The genetic vulnerability of Black Swans to H5N1 has been widely reported—unlike their northern hemisphere counterparts, Black Swans are missing some genes associated with immune function, possibility due to “limited pathogen challenge” in isolated Australia. How many other species in Australia may have similar genetic vulnerabilities? As BirdLife Australia’s Manager, Wetland and Migratory Shorebirds, Chris Purnell explains, “they’ve mapped the genome for Black Swans, which is why they know. But there are potentially other species in the same boat, but we just don’t know that yet.”

Watching out for birds

With spring nearly over, the riskiest time for bird flu may have passed us for another year. But Australia is a large country, and it’s possible the virus has arrived, and we just haven’t tested the right bird. That’s why BirdLife Australia’s network of volunteers and supporters can play a crucial role in managing a potential outbreak—with hundreds of thousands of people out and about watching birds, any suspicious behaviour or sick birds can be reported to the Emergency Animal Disease Hotline, and managed by authorities. Signs include abnormal posture, trouble walking, standing or flying, lack of coordination, sneezing and coughing, and swelling in the head or neck. Numerous dead birds in a single location are also a potential warning sign. Should you see sick or dead birds, remember not to approach or touch them, and report immediately to the Hotline on 1800 675 888.

At the end of the day, the best defense against contagious diseases in birds––even those ‘created’ by human actions such as H5N1––is healthy, diverse and thriving populations that are resilient enough to bounce back should disaster strike. Sadly, too few of our birds could be described in this way––through habitat destruction and damage, introduced predators, inappropriate fire regimes, the diversion of water from the environment and the ravages of megafires brought on by human-induced climate change, so many of our birds are living on the edge.

The One Health approach to public health that developed in response to diseases like H5N1 that spread between humans and animals is grounded in the idea that human, animal and environmental health are not just closely linked, but interdependent. One area cannot thrive at the expense of the others. Visiting this panzootic upon our birds––just the latest in a long list of human actions that have pushed wild birds towards extinction––might well end up being a plague on both our houses.