Expert Commentary: What’s going on with bird flu in Australia?

19 July 2024 Expert commentary

The world is currently experiencing a bird flu ‘panzootic’ – a pandemic of birds. This devastating global outbreak is being caused by a particular strain of highly pathogenic avian influenza (HPAI) virus called H5N1 clade 2.3.4.4b. It is affecting wild birds and poultry, and some mammals, on every continent except Australia. 

Meanwhile, three separate strains of bird flu – H7N3, H7N9 and H7N8 – have been detected across poultry farms in Australia.

As Australia’s national reference laboratory, CSIRO’s Australian Centre for Disease Preparedness (ACDP) is playing a key role in testing, determining virus strains and keeping Australian authorities informed.

All quotes below are available for use by media. They can be attributed to Dr Frank Wong, a senior research scientist at ACDP and a World Organisation for Animal Health (WOAH) Reference Laboratory expert in avian influenza.

What’s the difference between low pathogenic and highly pathogenic bird flu? 

“The virus strains are classified as either low pathogenic avian influenza (LPAI) or high pathogenic avian influenza (HPAI) viruses. LPAI infections in birds may cause only mild illness or no disease at all. But HPAI infections in poultry can cause outbreaks of severe disease, resulting in many sick and dead birds in affected farms. 

“Some H7 and H5 strains start out as low pathogenic in wild birds but they can become highly pathogenic through virus mutation in infected chicken flocks."

How much of a risk does highly pathogenic avian influenza virus pose to people? 

“Bird flu is basically a virus that affects birds with occasional spill over to other animal species. 

“There have been rare cases when people have caught the virus, usually from working directly with the infected poultry or affected farms.  

“As it is still a bird-adapted virus, we normally do not see avian influenza being transmitted from person to person or mammal to mammal. The risk to people is still considered low at this time.” 

Has Australia ever had an outbreak of bird flu before now? 

“Australia has had previous outbreaks of the disease ‘HPAI’ in poultry, including in 2012, 2013 and again in 2020. In each instance, the outbreaks were quickly contained and the strain causing the highly pathogenic outbreak was eradicated. 

“Australia’s previous outbreaks were of H7 bird flu; we’ve never had an outbreak of H5N1 here, which is the strain causing havoc overseas.” 

What strain of bird flu is causing Australia’s current outbreaks? 

"There are currently two states and one territory affected by bird flu outbreaks. While there are three separate strains involved, they are all H7 strains of the virus. Outbreaks in Victoria have been caused by H7N3 HPAI impacting egg farms in the Meredith region and H7N9 HPAI in one farm in the Terang region. 

"The HPAI outbreaks affecting farmed chickens in the Hawkesbury region of NSW and in the ACT have been caused by the H7N8 strain."

What strain of bird flu is causing the devastating outbreaks around the world? 

“The bird flu strain causing havoc overseas is known as highly pathogenic H5N1 clade 2.3.4.4b. It emerged sometime in 2020 and has spread to every continent except Australia, affecting millions of wild birds and domestic poultry. This virus has even killed wild birds and marine mammals in Antarctica.” 

What is different about this H5N1 strain? 

“Clade 2.3.4.4b H5N1 has picked up the ability to infect a much wider variety of bird species than other HPAI strains previously. 

“Scientists have also noted that wherever H5N1 spreads, it has mixed with local bird flu strains. This seems to have allowed it to adapt to new environments and may explain its ability to infect many new bird species. 

“It has also spilled over into several mammal species such as foxes, and marine mammals such as sea lions and elephant seals and on rare occasions it has spilled over into cats and dogs. It was reported in farmed minks and fur farms in Europe and since March this year, the virus was detected in dairy cows for the first time in the USA.” 

What is the risk that H5N1 will reach Australia? 

“The main hosts that carry bird flu viruses over long distances are migratory ducks and geese . As Australia isn’t in the flyways of these migrations, the risk of H5N1 reaching Australia is relatively low.  

“However, the risk has slightly increased because of H5N1’s ability to infect additional species of wild birds. This increases the chance of introduction through regional or bridging species.” 

What is CSIRO’s Australian Centre for Disease Preparedness in Geelong doing to prepare for a possible incursion of H5N1? 

“At CSIRO’s Australian Centre for Disease Preparedness, we assist with Australia’s surveillance efforts and conduct research to characterise the virus to understand it better. We’re helping keep track of bird flu and which strains are spreading through poultry and wild birds not only in Australia but in our region and globally. 

“Australian state and territory laboratories rely on ACDP to conduct testing on bird samples to confirm the presence of avian influenza.  

“We then do genetic sequencing of the virus and use this information to identify the exact strain and understand if and how it is changing. This way we know if the virus is a local virus already present within Australian wild birds, or whether it could be a strain introduced from overseas.  

“We then provide this information and advice to authorities and animal health working groups to support them in making decisions for responding to outbreaks.  

“In my role as the World Organisation for Animal Health reference expert, I meet with the other avian influenza reference laboratory experts. We share information about the circulating strains around the world and any new spillover events, such as the H5N1 infections of dairy cattle in the US earlier this year. 

“This work has also helped us be as ready as we can be with diagnostic capabilities and response advice.” 

For more information on the current disease situation visit outbreak.gov.au. This site has links to state and territory specific information, and information about how to protect your birds. 

Read more about ACDP’s research on bird flu dynamics in Australia.