Photo collage by Britt Wilkins. Image: Karen Moskowitz / Getty Images.

For years, Australia was something of an outlier in the global H5N1 crisis, managing to avoid the highly pathogenic strain of influenza that had swept through wild birds, poultry and many mammals across the world.

That all changed in June of this year: H5N1 has now established itself in Australian wildlife, with local transmission confirmed and cases now spreading across several states.

Professor Kirsty Short is an NHMRC Senior Principal Research Fellow at UQ. She researches viral immunity and pandemic preparedness, and provided expert guidance to the Australian government during the COVID-19 pandemic. She spoke to Contact about what Australians should and shouldn't be worried about in the face of the H5N1 avian influenza threat.

 

How worried should we be about the bird flu threat at this stage?

It depends on what perspective you're thinking about. If you're thinking about public health and human health, I wouldn't be so worried because the risk is low, and we've seen that in other countries as well. If you're thinking about poultry and the economy, I'd be somewhat worried.

But if you're thinking about biodiversity and native species, I'd be very worried.

We've now seen the first recorded case in a wild mammal. While not surprising, this is a concerning development in the spread of the virus among Australian wildlife. 

Can you tell us a bit about H5N1, how it spreads and why it's proven so difficult to contain?

H5N1 first emerged in southern China in 1996, and from there it spread around the world. As it spread, it kept changing through a process that influenza viruses can undergo called reassortment.

That's where 2 viruses co-infect the same cell, mix and match their genetic material and create a new virus. This process kept happening over time, so the virus diversified and diversified. Then, in 2020, we saw a new clade, or strain, of H5N1 emerge in the Netherlands called 2.3.4.4b.

This particular strain seemed to be very adept at spreading. It rapidly spread through North America, reached South America, then Antarctica and eventually Australia.

What’s unique about this strain is how effectively it spread across countries. It was also quite unique in how many animals it could infect. It wasn't just infecting birds. We were also seeing infections in marine mammals and scavenger animals.

Could bird flu begin spreading between people or even trigger another pandemic?

At the moment, I think it's a low risk.

What we've seen overseas is that human infections have occurred, but they've generally been in people who have really close contact with infected animals, whether that's poultry or cattle.

When H5N1 first emerged and infected humans, it had about a 60% mortality rate. This new strain is much lower, probably around 3%. A lot of people experience mild illness, predominantly conjunctivitis.

It doesn't seem to be very adept at infecting humans, and it certainly can't spread efficiently from human to human. From that perspective, it's not a likely pandemic candidate.

My concern is that the more species this virus infects, particularly mammalian species, the more opportunities it has to evolve and become mammalian-adapted. That's why, from a human health perspective, we should really limit the spread of this virus among our native species.

What should people know about human infection and symptoms?

At the moment, the people who should be most aware of symptoms are those in high-risk occupations. That includes poultry farmers, people working closely with birds and people undertaking sampling activities.

The symptoms are generally typical flu symptoms, but there is also this presentation of conjunctivitis. Some people don't have symptoms at all.

As I said, this strain appears much milder than the initial version of the virus. Right now, the human risk is very low.

Why are experts relatively reassured about the current risk to humans?

Some people argue that this virus can never become a pandemic because it's been around since the 1990s and still hasn't acquired the ability to spread efficiently from human to human, which is what you need for a pandemic.

There's also probably some level of cross-protective immunity in the population because the seasonal influenza virus H1N1 has an N1, and H5N1 also has an N1. There is some cross-protection between those N1s. It's not great, but it's something.

So, there are some things on our side. The difficulty is predicting how the virus will evolve now that it's in Australia and has the potential to be exposed to a whole range of different species it hasn't encountered before.

Can people catch bird flu from eating chicken or handling eggs from the supermarket?

No.

First of all, H5N1 is not in our poultry population, so people shouldn't be worried about that right now. Influenza is also a relatively easy virus to kill. You can't get it from eating properly cooked chicken – and hopefully nobody reading this is eating uncooked chicken!

There was a case overseas involving someone who became infected after consuming the blood of an infected animal, but again, that was uncooked. Cooking really makes the difference.

You mentioned biodiversity and the economy as bigger concerns. What does a worst-case scenario look like?

The absolute worst-case scenario is that we lose species. Australia already has a very bad track record of species loss and biodiversity loss, so there is a possibility that this could prove to be a tipping event for some species.

If this virus gets into poultry farms, it'll also be devastating for that industry. It's terrible for individual farms and it also has significant trade implications because Australia would no longer be classified as H5N1-free.

We've seen the consequences overseas. This virus has resulted in the deaths of more than 300 million poultry animals worldwide, and that's probably a gross underestimate.

I don't think we can understate the impact this would have on poultry production and the economy if it became established in poultry farms.

Finally, if someone comes across a sick or dead bird that they're concerned about, what should they do?

Don't approach it and don't touch it.

Simply report it through the relevant hotline and follow the advice you're given. Authorities will be able to guide you on any further steps that may be required.