The world is currently grappling with another pandemic — but this time it's affecting animals.
The highly pathogenic avian influenza resurfaced in Europe in 2020, and four years later, the H5N1 strain has spread to every continent except parts of Oceania.
However, Australia has detected other strains, with fresh reports surfacing just this week. So, how worried should we be about it reaching New Zealand?
What's the latest down under?
This week, a Sydney chicken farm made an unwanted detection of avian influenza, leading to the culling of all their birds.
"I feel for the farm and especially for the workers who are having to carry out this work but it is essential for us to protect the biosecurity of New South Wales," Australia's Agriculture Minister Tara Moriarty said.
New South Wales is now the second state in a month to report avian influenza, following Victoria, where seven farms had infections.
Both states have identified different strains than the one causing the most alarm globally.
Veterinary Public Health & Food Safety professor Michael Ward said, "It's actually something we haven't seen before, this many viruses in this many farms."
How did it start?
Most avian influenza viruses are of "low pathogenicity", meaning they are not highly contagious and commonly infect wild birds like seagulls. However, this changes when H5 and H7 viruses infect poultry, such as chickens, mutating and potentially becoming highly contagious and deadly.
The H5N1 strain was first detected in Hong Kong in 1997, infecting and killing humans.
It resurfaced in China in 2003 and spread rapidly across Asia, the Middle East, the Americas, Europe, and Africa.
While the outbreak wasn't the end-of-the-world event many feared, it still resulted in the deaths of hundreds of millions of birds and caused vast economic losses due to a global halt on poultry trade.
How does it spread?
It comes as US officials try to work out how a Texas man contracted the virus from an infected cow. (Source: 1News)
During the current outbreak, bird-to-human transmission has been rare.
The virus spreads by direct contact with infected birds or their bodily fluids and can also be contracted through indirect contact with droplets or dust.
There is no record of human-to-human transmission.
Tedros Adhanom Ghebreyesus, the director-general of the World Health Organization (WHO), said the WHO "continues to assess the risk to public health as low".
What about the strains?
The most well-known strains, H5N1 and H7N9, are serious, can spread to humans, and can be deadly.
While today's H5N1 variant hasn't been detected in this part of the world yet, the H7 strains found in Australia have already led to the euthanisation of more than a million chickens and ducks, causing significant economic loss.
The ongoing culls have not yet led to an egg shortage, but retailers have imposed purchase limits in anticipation. The uncertainty about how the virus is spreading keeps experts, farmers, and authorities on edge.
What does this mean for New Zealand?
Virologist Jemma Geoghegan told Breakfast the virus usually travels "by wildlife, usually wild birds". (Source: Breakfast)
While New Zealand has not yet detected any cases of these strains, experts warn that it is only a matter of time.
Experts say continuous monitoring and strict biosecurity measures are essential to prevent an outbreak. And if it were to happen, the economic impact on New Zealand's poultry industry could be significant, similar to what Australia is currently experiencing.
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