Science Deadline: How worried should Australia be about bird flu right now?

Bird flu has hit the Australian headlines this week, with Victoria's health and agricultural departments announcing two unrelated incidents of avian influenza and a third incident in WA reported today.

On Tuesday, the Department of Health reported a case of H5N1 avian influenza in a child who was sick in March 2024 after returning from overseas. The next day, Agriculture Victoria announced it was investigating the deaths of chickens at an egg farm near Meredith, with testing revealing it was not the highly pathogenic strain causing concern overseas, but the H7N3 strain of avian influenza. A second farm linked to the Meredith property has now also had confirmed cases of the virus and there are reports of a different, less contagious strain, H9N2, at a farm in WA.

The human case is the first ever reported in Australia, however the Department is confident the illness was just a single case as the virus does not pass between humans easily.?

"There is no evidence of transmission in Victoria and the chance of additional human cases is very low," the Department said in a statement.

The news is less positive for the chicken outbreak, at least for the chickens.?Professor Raina MacIntyre from the?Kirby Institute told the AusSMC the economic impact of avian influenza if it spreads through farmed poultry is "enormous" and cause for concern, even if the threat to humans is minimal.

"Traditionally, outbreaks in farmed poultry have been managed by culling infected birds, and this tends to control the outbreak. Fortunately, we do not have widespread infection in Australia, so this should be a feasible strategy," Prof MacIntyre said.

She said currently avian influenza does not pass easily to and between humans because it is adapted for bird respiratory tracts, however, experts fear the virus may one day mutate to better infect humans.

"H5N1 clade 2.3.4.4b is the most concerning, as it has caused severe disease, including neurological damage, in animals and birds, and the statistical probability of it mutating to become transmissible in humans (and thereby cause a pandemic) is higher than any time in the past, because of the sheer scale of global infection in animals and birds and the opportunities for human adaptation," she said.

"Once it gets in the food supply (meat, unpasteurised milk), that risk is even higher. A human pandemic of influenza would be much more severe than SARS-CoV-2."

Dr Kirsty Short from the University of Queensland said it was?very reassuring that the strain identified in Victoria is an H7 virus rather than the problematic H5N1 strain that is circulating globally.

"However, this should serve as an important reminder as to the need for constant vigilance regarding avian influenza and the need to report any sick or dying birds to the appropriate authorities," Dr Short said.

H7N3 is still serious for the birds, and Professor Bob Doneley from the University of Queensland said this was the ninth outbreak of a strain considered to be a highly pathogenic avian influenza (HPAI), with the potential to do major damage to bird populations, since 1976.?

He said while Australia has still not had to contend with the more dangerous H5N1 in birds here, these outbreaks have put us in a better position to handle it when the inevitable happens.

"While Australia has not experienced an outbreak of the HPAI H5N1 virus, the experience gained from dealing with the outbreaks of other strains of HPAI over the last 50 years has given Australian scientists invaluable opportunities to learn how to deal with future outbreaks – even of the H5N1 variant. Surveillance of wild birds and domestic flocks, as well as contingency plans to stop an outbreak in its tracks, are not only in place but have been tested and we know they work," Prof Doneley said.

Dr Robyn Alders, Honorary Professor at the Australian National University, said Australia's previous success at handling outbreaks is in part due to a good relationship between health authorities and local poultry farmers.?

"Producers know that if [a highly contagious strain] is confirmed, that they will receive compensation from the government following the implementation of control and containment procedures," Dr Alders said,

"This prior agreement is one of the major reasons why the control of HPAI has been so successful in Australia compared to many countries in the region ?However, we now have many more households raising backyard chickens and it's important that these households ensure that they provide their chickens with treated/tap water and feed in containers inaccessible to wild birds."

She said chicken owners should contact a vet or the government Emergency Animal Disease Hotline if their chickens show the following symptoms; "sudden death,?swollen head,?closed and runny eyes,?lethargy and depression,?lying down and unresponsiveness, lack of coordination and eating less than usual."

You can read the full Expert Reaction here

This article originally appeared in Science Deadline, a weekly newsletter from the AusSMC. You are free to republish this story, in full, with appropriate credit.?

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By Rachel McDonald, the Australian Science Media Centre