The CSIRO is tracking Bird Flu as it transmits within Australia. Here’s what we know.

For the past six years, the world has been affected by a highly pathogenic strain of Avian influenza H5N1 — what virologists are calling HPAI H5N1Clade 2.3.4.4b.

Travelling with sea birds, the strain moved from Europe, through Asia, to North America and South America in 2021-22, and eventually landed in the sub-Antarctic.

It reached the Australian external territory of Heard Island in late 2025, appearing in both sea bird and elephant seal colonies. 

H5N1 was detected in Western Australian wild birds in June this year. It has since been detected all states and Territories (aside from the Northern Territory).

There have been several mass mortality events in wild birds.

“The genotype that we're talking about for Australia is what is known as B3.2,” said CSIRO Senior Research Scientist, and World Organisation for Animal Health (WOAH) Avian Influenza expert, Dr Frank Wong.

“It caused great impact to South American poultry industries, as well as to wild bird life and to marine mammals,” said Wong. 

The risk to birds — wild, captive, or agricultural — is significant.

The risk to human health of H5 bird flu remains low. 

An ‘ecological perfect storm’

Dr Debbie Eagles is Director of the CSIRO’s ACDP.

The ACDP conducts diagnostic testing and characterisation to identify transmission, changes in the virus, and new strains emerging.

‘Importantly, we provide a 24-7 diagnostic service for avian influenza … for those results to get to decision makers in a timely manner,” said Dr Eagles.

“What keeps me up at night is certainly what this means for our native wildlife.”

Dr Wong said that a high avian mortality rate could occur in Australia, as it did in North America and South America.

“Chickens in particular are very susceptible to highly pathogenic bird flu viruses,” he said.

On a world scale, since 2001, “efforts to control the high pathogenic strains of bird flu have resulted in the destruction of more than 400 million chickens” worldwide, reported the ABC.

5.61 million chickens died or were culled during March 2026 alone.

Dr Wong says that infection of livestock in Australia on the scale seen in other countries, is unlikely.

In what was likely a single introduction from wild birds to US dairy cattle in late 2023 or early 2024, the B3.13 genotype of H5N1 has become endemic in bovines in the United States, causing significant mortality in livestock and poultry.

“The South American and sub-Antarctic islands genotype (which travelled to Australia) hasn't been associated with infection in cattle. The genotypes infecting dairy cattle in the United States (B3.13 and D1.1) have not been detected outside the United States,” said Dr Wong.

“You would need an ecological perfect storm for the virus to spill over and impact livestock.”

“It certainly can infect marine mammals… on Heard Island, up to 75% of the season's juvenile population succumbed to H5N1 infection. But the risk is still considered low for infection of livestock.”

H5N1 has not yet been detected in poultry, or livestock, in Australia.

What’s the human risk?

According to the World Health Organisation (WHO), while avian influenza viruses do not currently transmit easily from person to person, the viruses do have potential to mutate to become more contagious.

“To date, there's no clear predictor for the ability of this virus to jump from birds to mammals … to humans. It’s very much an avian-adapted virus with majority avian genetic signatures,” said Dr Wong.

“The risk [of infection] is low, and predominantly, the disease is mild.”

The cumulative number of confirmed human cases of avian influenza A(H5N1) reported to the World Health Organisation (WHO) between 2003-2026 is 1000; of those cases, 479 have resulted in death.

A University of Toronto study notes that, ‘although morbidity and mortality in humans with the HPAI H5N1 clade seems to be limited to date, previous HPAI H5N1 viruses have been associated with mortality rates of approximately 50% in humans.’

In the Western Pacific Region, from 1 January 2003 to 7 July 2026, a total of 485 cases were reported from six countries. Of these cases, 320 were fatal, resulting in a case fatality rate (CFR) of 66.0%.

The only confirmed human case of HPAI-H5N1 in Australia was a 2.5-year-old girl who contracted the virus in Kolkata India in 2024.

Trial vaccinations

The CSIRO trialled an H5 vaccine for smaller birds last year.

“Those trials provided important safety and efficacy data for smaller birds. The vaccines were initially developed for poultry and are being adapted globally for use in wild bird species,” said Dr Eagles.

State and Territory governments have begun vaccinating captive bird populations against H5N1. 

“There's only so much that we can do to protect our broad-scale wildlife, and that's certainly concerning,” said Dr Eagles.

“The vaccine is injectable. It is important to give a second dose to get the full and longer-term immunity. With that in mind, obviously captive threatened species are a better vaccine target.”

Victorian wildlife officers are vaccinating fairy penguin colonies in Victoria to prevent a ‘worst-case prediction’ mortality events. 

What should health care professionals look for?

While including the caveat that they are not health care professionals, the CSIRO experts suggested the standard flu vaccine for all patients, as avoiding the flu would make it easier to identify H5N1 symptoms.

Dr Wong told GPs what symptoms to look out for. 

“So, people who present with flu-like symptoms and report exposure to wild birds that have been sick, potentially ones that have tested positive,” he said.

“We’ve seen that risk is very low for transmission between birds and people.”

The University of Toronto study noted that, “historically, influenza A(H5N1) presentation in humans has included severe respiratory disease with gastrointestinal and neurologic involvement. Cases associated with the current outbreak have largely been mild, with most patients demonstrating conjunctivitis and respiratory symptoms,” it reads.

Dr Eagles, who played a pivotal role in CSIRO’s response to COVID-19, says that the ACDP works closely with health care.

“We engage significantly with the public health lab networks. We’ve been fortunate in being the last continent to have H5N1. We’ve had that time to prepare.”

If you notice sick or dead birds or other animals, you should not touch them. Report to the 24-hour Emergency Animal Disease Hotline on 1800 675 888.

For more information visit the Australian Centre for Disease Control.