Expert reaction: Bird flu outbreak

Bird flu hit the headlines this week, with Victoria’s health and agricultural departments announcing two incidents of avian influenza and a third incident in WA reported at the end of the week.

On Tuesday, the Victorian Department of Health reported a case of the highly pathogenic and deadly 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 H7N3 strain of avian influenza which caused the deaths of chickens at an egg farm near Meredith. It was not the highly pathogenic strain which has been causing concern overseas.

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

“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. It was reported that within days of the outbreak 500,000 chickens were culled.

Professor Raina MacIntyre from the Kirby Institute in the “expert reaction” colated by the Australian Science Media Centre (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 says.

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 says.

“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,” Short says.

H7N3 is still serious for the birds, and Professor Bob Doneley from the University of Queensland says 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 says while Australia has still not had to contend with the more dangerous H5N1, 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 says.

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.”

Explainer: Bird flu