There's a new outbreak of bird flu in Australia. Here's what you need to know

The Guardian

10-02-2025

A new outbreak of bird flu has been detected in Australia, with authorities confirming an outbreak of H7N8 avian influenza at an egg farm in northern Victoria at the weekend.
The detection comes only weeks after quarantine restrictions were lifted on the last property affected by Victoria's 2024 avian influenza outbreak – Australia's largest on record.
Increases in egg prices and ongoing shortages have made headlines in both Australia and the US in recent months.
In the US, however, the culprit is a different subtype of the virus – H5N1, which has wreaked havoc globally and has experts worried about the potential for another human pandemic.
The bird flu outbreak was detected at a poultry farm in Euroa, in north-eastern Victoria. Testing has confirmed it is H7N8, a type of highly pathogenic avian influenza, which means it can cause severe outbreaks of disease with many sick and dead birds.
It is different from another H7 strain that affected Victorian poultry farms during 2024's outbreak, which was eradicated.
In mid-2024, there were outbreaks of H7 bird flu strains across south-eastern Australia at eight premises in Victoria, six in New South Wales and two in the Australian Capital Territory. Of these, 11 were commercial poultry farms. An estimated 1.8 million birds were culled last year at infected farms, resulting in fewer hens and a drop in egg production.
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The NSW and ACT outbreak was also caused by an H7N8 virus, but Agriculture Victoria confirmed the current Victorian outbreak was unrelated to those two.
Historically, H7N8 has not been a dominant strain globally, nor is it widely associated with human infection, said Assoc Prof Vinod Balasubramaniam, a molecular virologist at Monash University Malaysia. The source of such outbreaks is usually from migratory birds, he said.
'These avian flus are normally present in the waterfowl population – ducks and geese, that sort of thing,' Dr Jane Younger, a lecturer of Southern Ocean vertebrate ecology at University of Tasmania, said. 'What has happened is these viruses have spread into poultry, mutated into these highly pathogenic forms, and then spread back out into wild populations.'
In the US, a bird flu outbreak has ravaged poultry flocks since October, driving the price of eggs up. Since January, about 14.7 million egg-producing chickens have been affected in the US, exceeding the total numbers of hens affected in all of 2023.
But the culprit there is a different subtype, H5N1, which has been in the US for years and has caused outbreaks globally since 2021.
A particular group of H5N1 viruses, known as clade 2.3.4.4b, has decimated wild bird populations in the UK, across Europe, South Africa and the Americas, killing tens of millions of birds. It has also killed tens of thousands of seals and sea lions, and has infected at least 48 mammal species.
'Australia at the moment is the only continent that is free of that particular strain,' Younger said. H5N1 was detected in Antarctica for the first time in 2023 and can be spread across thousands of kilometres by migratory birds.
'None of us know if or when it will reach Australia,' Younger added, calling it 'definitely something we need to prepare for'.
To date, H5N1 has mostly affected the agricultural sector and wildlife. But its ability to infect humans has virologists worried.
The US has recorded 67 human infections since 2024, while Australia has reported a single case, in a child returning from India last May. Research, however, suggests that many human cases go undetected.
Though no clear human-to-human transmission of H5N1 has been documented yet, scientists are on high alert. In the last year, H5N1 has jumped to other domesticated species in the US, including cows, goats, pigs and cats.
'We know that it's highly pathogenic in nature, it's highly evolving,' Balasubramaniam said of H5N1 2.3.4.4b. 'I think it is the dominant strain of global concern.' Unprecedented spread, infections in mammals and new genetic changes need immediate scientific and policy attention, he said.
'It ticks all the boxes for the virus to have pandemic potential,' Balasubramaniam said. 'The only thing it lacks is the mutation which enables it to be airborne and to be transmitted human to human.'
In October, the Australian government announced it would invest $100m to strengthen surveillance and biosecurity responses against H5N1.