‘The ramifications are huge’: Why scientists fear havoc when H5N1 bird flu strain reaches Australia

In the small country town of Meredith, about 70 kilometres west of Melbourne, a lone dead tree stands in the centre of a paddock, looming over two long red furrows clawed into the ground.

Underneath the turned earth of these twin 200-metre graves lie about 1.3 million dead chickens.

They are the total Victorian casualties of Australia’s worst avian influenza outbreak.

Across the country, outbreaks of three different strains of bird flu were discovered in 16 farms across three states between May and July this year.

Almost 2 million chickens were killed.

Just a few paddocks south of the Meredith mass grave, Brad McAuliffe is standing by a fence line, separated from his Moorabool Valley Eggs sheds by a few hundred metres, a beaten-up “no entry” sign strung across the road and strict Agriculture Victoria biosecurity measures.

Mr McAuliffe is the owner of both Moorabool Valley Eggs and AVGO Eggs, and is also proof that lightning can strike twice.

His farm here in Meredith was hit by an outbreak of the H7N3 strain of Avian influenza, confirmed on May 22. A day later, one of his farms in Terang, 110km away, was hit by a completely separate strain of the virus, H7N9.

About half a million of his “girls” had to be euthanased across the two properties.

Stone-faced, he says the farms “both copped it”.

“It stopped our business completely,” he says. “We went from big revenue business, turnover, employing 40 or 50 staff, to nothing.

“As for the egg producing — buying and selling eggs — it’s just stopped everything and been absolutely devastating for us.

“[The cost to the business] is in the tens of millions. It’s something that we’ll never recover from.”

Agriculture Victoria’s director of animal health and welfare, Les Howard, is a serious man.

He’s just spent most of this year trying to lead Victoria’s response to avian influenza outbreaks, and says the state is “finally on the home stretch”.

“This current outbreak, we are currently in the cleaning and disinfecting stage for most of the farms,” he says.

“With the intent that most of those farms will be into their empty period and sentinel bird period hopefully within the next few weeks, and hopefully with commercial restocking to occur later in the year.”

But, this apparent good news comes with a caveat.

Something much worse is on the horizon.

What is H5N1?

H5N1 is the deadliest strain of bird flu and is currently wreaking havoc around the globe, causing outbreaks on every continental land mass except Australia — for now.

Avian Influenza has dozens of different strains. Australia’s 2024 outbreaks were all subtypes of the H7 strain — H7N3 in Meredith, H7N9 in Terang and H7N8 in farms in New South Wales and Canberra.

The main factor in the viciousness of the virus is whether it is low pathogenicity avian influenza (LPAI) or high pathogenicity avian influenza (HPAI).

Both can spread quickly, but LPAI strains cause little to no signs of disease in birds, while HPAI strains — such as those that made their way to Australia this year — cause severe disease and high mortality rates.

HPAI strains often kill almost all infected chickens within about 48 hours.

While the different avian influenza strain numbers might not mean much to the average punter, there is one combination the Australian public may soon become very well acquainted with: H5N1.

It is the worst of the worst.

Not just chickens get avian influenza: wild birds carry the virus, exacerbating its spread as they move between areas and even countries.

A recent mutation in the H5N1 virus, designated “clade 2.3.4.4b”, has spread around the world like wildfire since 2020, killing about 2 billion chickens and spilling over into more and more species of birds and even mammals.

In the US, the virus’s spillover to other species has hit cattle, infecting 238 dairy herds across 14 states. While cows do not need to be euthanased after being infected with avian influenza, the outbreak can cause reduced production and put economic strain on farmers.

In South America, H5N1 has spread aggressively amongst wildlife since 2022, killing about 17,400 elephant seal pups in Argentina, 32,000 sea lions, 4,000 Humboldt penguins and 62,000 Peruvian pelicans — amongst many other animals.

The spread of H5N1 via migrating birds also meant the virus made its way to Antarctica this March. 

It’s understood it was carried there by wild birds from the coast of South America and has already caused numerous “mass mortality” events in populations of penguins and wild birds.

Back in Meredith, Les Howard shares a sobering prediction about H5N1’s potential of making it to Australia.

“It’s a matter of when it turns up, not if it turns up,” he says.

“And the likely prediction is it could occur in spring, with the migratory birds — but it could also happen any time of the year.

“H5N1 is different to the H7 strains which we’re currently responding to, in that it not only affects poultry, but it also affects wild birds and also mammals.

“So the impacts of an H5N1 outbreak will be significantly higher [than H7] in that it’s not just commercial farms or backyard birds that are affected — it very much will have major effects on our wildlife and native species.”

Our front line of defence

If — or when — H5N1 makes it to Australia, it’s likely the final confirmation may occur at the CSIRO’s Australian Centre for Disease Preparedness (ACDP), stationed on the shore of Corio Bay in Victoria’s largest regional city, Geelong.

Think about some of the worst infectious diseases you know: they’re almost certainly held in this facility.

Anybody entering the highest level of containment at ACDP must strip off, pass through an airlock and change into hospital scrubs on the other side.

Airlocks are at the entrance of most main labs, and those leaving the containment area require a shower before returning to the outside world.

Little is allowed to exit the containment area, apart from well-scrubbed humans.

Here, scientists like Jasmina Luczo, the team leader of avian infectious diseases research, dedicate much of their time to understanding avian influenza: tracking it, and testing samples sent in from around the country to confirm or rule out the presence of the virus.

Much like Les Howard, Dr Luczo expects one of those samples to test positive for H5N1 in the near future.

“Researchers are really tracking it closely about the when, rather than if,” she says, sitting in one of the spotlessly sterile labs in the highest-security section of the facility.

“If it does get here, it will be pretty devastating. It has the ability — as we’ve seen overseas — to kill numerous species of birds and mammals, so in line with what we’re seeing overseas, we’d expect the same thing to be occurring here.

“We have unique flora and fauna in Australia, and so if [H5N1] bird flu was to arrive and to infect our threatened species populations, we could potentially lose them, and that could be devastating for the ecosystem and for our future.”

That potential devastation of our wildlife is reason enough for Australians to pay attention to H5N1, Dr Luczo says.

“The ramifications are huge.

“This virus is a game changer. So, everything that we thought about it, it’s just changing. It’s doing unusual things. We need to be prepared, and now.”

If the first positive Australian sample of H5N1 is sent to the ACDP, it is likely the team leader of sequencing, Matthew Neave, will be one of the first to confirm the virus has made it to our shores.

“I think it would be a pretty big day for us here, probably pretty sad really for the Australian wild birds and poultry communities,” Dr Neave says.

Sitting in a different, but equally sterile lab, he echoes Dr Luczo’s concerns for the country’s native wildlife.

“It’s a big deal,” he says.

“I mean as we’ve seen from overseas, we’ve had millions and millions of birds killed, it’s also now spreading in mammals, it’s causing a lot of issues there, and so you’d assume something similar might happen in Australia.”

“This is going to have a big impact, people should care about this, it really will be devastating for our environment.

“I think that’s why we need to be worried about it. We need to really prepare for it.”

What’s at risk

Expert warnings about Australian wildlife at risk of being decimated by H5N1 have made regular headlines this year, as the potential arrival of H5N1 looms over Australia.

Images of Tasmanian devils, seals and sea lions, black swans and many other species often accompany these warnings, leaving the Australian public to wrestle with the potential of “mass mortality events” hitting some of its beloved wildlife.

A 2023 study in the journal Genome Biology, for instance, found an outbreak of H5N1 in Australia would put black swans in “significant peril”, after genome sequencing found “the black swan is extremely sensitive to highly pathogenic avian influenza”.

While the risk of death for Australian wildlife is high, the risk for humans is less so.

The virus can kill people and has a high mortality rate, but it rarely makes the jump from animals to humans.

According to World Health Organization data, about 900 cases of human infection with H5N1 have been reported from 24 countries since 2003, with 463 of those cases fatal.

Instead, the human risk with H5N1 is very much an economic one.

The average Australian eats 15kg of eggs and 50kg of chicken meat every year, with the poultry industry worth about $3 billion annually.

The main control measure used when avian influenza is discovered in a chicken flock is a simple, blunt instrument: they are all euthanased.

It takes months to clean up chicken sheds and fields, and eventually bring in more birds to get back to producing eggs and meat, resulting in significant supply disruptions.

The loss of production represents a major economic risk to Australian chicken growers if H5N1 arrives.

It also has an obvious flow-on effect for people not directly involved in the sector — potential shortages of eggs and chicken meat.

Even now, four months after the outbreak of H7 strains, egg supply disruptions continue, with empty shelves still visible in some supermarkets.

What are we doing to prepare?

With spring now in full flight in Australia, the country is bracing for a potential arrival of H5N1 on the wings of a migrating bird — whether that be from the northern migration routes, or Antarctica in the south.

The federal government this month wrapped up an exercise wargaming the potential arrival of H5N1 in Australia, dubbed Exercise Volare, using the Italian word for “fly”.

The exercise included three scenario-based discussions using a hypothetical detection of H5N1 in Australia, involving representatives from governmental agriculture, environment and health portfolios, along with respective stakeholders.

Federal Agriculture Minister Julie Collins says the $7 million exercise is a sign of the prominence the government placed on being ready for H5N1.

“It’s about making sure that we’re better prepared.”

Ms Collins says it’s about ensuring Australia has systems and processes in place so that if the strain arrives, a potential outbreak can be contained, and anyone affected alerted in the fastest time possible.

“We can’t stop migrating birds, and if it gets to Australia it is most likely to come through migrating birds,” she says.

“What we want to do is make sure that if it gets here, we minimise the impact on the Australian economy and the Australian people, and of course our environment and our wildlife, and our flora and fauna.”

Ms Collins says when it comes to H5N1, it’s important for the Australian public “to be aware but not alarmed”.

And for chicken growers like Brad McAuliffe back in Meredith, the potential impact of H5N1 in Australia remains a daunting unknown.

“How long’s a bit of string, unfortunately,” he says, as the chicken sheds standing behind him remain empty.

Anyone who finds wild birds suspected of having bird flu should not handle them, but instead call 1800 675 888.