Virus in the sky
More than half a billion chickens are dead. That’s the number of farmed poultry that have died or been culled since 2005 in desperate attempts to halt the spread of a deadly influenza virus rampaging through the animal world. But beyond the devastating impacts on agriculture, it’s the disease’s effect on wild birds and mammals that has conservationists and biologists worried.
A slow burn, then a wildfire
This panzootic (a pandemic affecting animals) started slowly. In 2003 an avian influenza virus that hadn't been seen since 1997 re-emerged in Asia. Between 2005 and 2020 the virus bounced around Asia, Africa, Europe, the Middle East and North America, mutating and evolving as it mixed with influenza viruses in the local bird populations.
In 2020 a new strain, called H5 2.3.4.4b, started to spread in the global east and Europe. But this supercharged strain was not only killing poultry. Strangely for a high pathogenicity avian influenza, it also affected a wide range of wild birds, as well as wild mammals like seals, foxes and bears – animals that prey on birds. And they were dying, sometimes in huge numbers.
The new virus reached North American wild birds and poultry in 2021 and has since gone on to infect cats, dairy cows, farmed mink, skunks and other mammals. Over 35 mammal species have now been infected globally, often with fatal consequences. In 2022, the virus reached South America with catastrophic results. A mass die-off in wild birds occurred, including pelicans, cormorants and boobies; researchers estimate more than 200,000 birds perished. The deaths of thousands of sea lions exposed to infected birds followed, a devastating wild mammal mortality event on a scale never before seen with avian influenza.
It's now 2024, and avian influenza has reached both the Arctic and Antarctic – the first time in history that an influenza panzootic has spread to both polar regions.
Global distribution of avian influenza viruses with zoonotic potential observed since 1 October 2023. Red marks are the new H5N1 virus.
Source: FAO, used under Open Access policy. Accessed 25/4/24 Click here for original
Why is this virus so devastating?
Influenza is one of the most studied viruses on earth. We know that shorebirds (like gulls and terns) and waterbirds (like ducks and geese) naturally carry harmless low pathogenicity influenza viruses. Typically, poultry outbreaks occur when these low pathogenicity viruses gain access to poultry farms. The crowded, high-stress environment of a modern-day industrial farm provides the perfect conditions to ramp up viral mixing and evolution.
New, highly pathogenic strains can emerge within days in such farms. While these can rapidly kill whole flocks, the disease is not usually able to re-establish itself in wild birds. In contrast, the current panzootic has been driven by this particular virus’s ability to sustain infection in a wide range of wild birds, which then carry the virus with them as they follow their natural yearly cycles of migration.
The effects of highly pathogenic avian influenza on wildlife and poultry have been unprecedented in scale and spread.
​
Content warning: This slideshow include images of deceased animals and agricultural operations.
Source: Getty Images, used under Terms of Use policy. Accessed 25/4/24 Click here for original
What is the risk to Australia?
Australia remains the only continent free from the new strain of avian influenza, a gift of our geographic isolation. Even though migratory seabirds can carry influenza viruses, Australia has never detected an incursion of exotic influenza strains through these seasonal visitors. Rather, our domestic avian influenza outbreaks have been few (just 8 between 1976 and 2020), and have followed the usual pattern of low pathogenic influenzas from local waterbirds gaining entry to poultry farms and evolving into highly pathogenic strains.
The risk from wild birds carrying highly pathogenic avian influenza is new, and represents a worrying change in disease behaviour with epidemiological implications that are yet to be fully understood.
​
These new conditions mean that Australia’s risk rating for highly pathogenic avian influenza in wild birds was upgraded to high in April this year. Likewise, the risks to our domestic poultry industries (worth AU$5 billion annually) and our local fauna are also increased, complicated by our still-incomplete knowledge of how this virus might behave in marsupial species and our unique birdlife.
​
What are the human risks?
Highly pathogenic avian influenza has caused more than 800 human infections since 2003, typically in people who had close contact with infected animals. While many had mild illness, 463 people have died, a case fatality rate of 52%. Only a low number of human cases have been due to the new H5 2.3.4.4b strain.
At the moment, the virus is not able to pass directly from one person to another, so a human pandemic is unlikely. The concern is that if further mutations occur, a newly evolved strain will gain this ability. Mixing with other influenza viruses, particularly in hosts such as pigs, can encourage this kind of dangerous viral evolution.
Fortunately, recent research suggests that current influenza vaccine technology and treatment options should be effective against the new H5 2.3.4.4b strain.
​
While the human health risk is currently low, human impacts of the current outbreak have been severe and include economic and agricultural losses, trade disruption, disrupted egg and meat supply, and the mental health impacts of mass cullling of farmed birds.
What happens next?
Australia has a well-established network of viral surveillance programs aimed squarely at detecting influenza (and other viruses) in wild birds. More than 135,000 wild birds have been tested since 2005.
Disease response plans are in place to protect the poultry industry if avian influenza does reach our shores. Hearteningly, a plan to protect our unique wildlife has also recently been developed by Wildlife Health Australia.
Government and industry preparations are ongoing, but the key to early detection of avian influenza's arrival in Australia will be public awareness. Information is starting to filter down to the general public through news articles such as this SBS Australia explainer report, but media coverage has been lacking. Increased community awareness is the best defence against the infection getting a foothold in Australia's unique ecosystems.
What can you do to help?
Report
If you see any unusual bird mortalities, report them by calling the Australia-wide, 24 hour Emergency Animal Diseases Hotline.
​
1800 675 888
​
To protect yourself, follow Wildlife Health Australia's Advice for people who encounter sick or dead wild birds.
​
Follow
Keep up to date with the latest news by following some of the animal and human health organisations listed below.
Talk
Talk to your friends and family that have backyard chickens or hobby farms. Help raise awareness of the risks of avian influenza reaching Australia and the importance of biosecurity.
Want to know more?
Up to date information can be found at the World Organisation for Animal Health (WOAH), World Health Organization (WHO), Wildlife Heath Australia (WHA) and the Australian Government agriculture site.
​
Read Australia’s avian influenza response plans for domestic animals and wildlife.
Track human cases of avian influenza at the WHO.
Track animal cases of avian influenza at the WOAH and United Nations Food and Agriculture Organisation (FAO).
See a list of all animals affected by the new H5 2.3.4.4b strain of avian influenza.
​
Hear from the Australian scientists conducting viral surveillance of wild birds.