Michelle is monitoring an unfolding avian catastrophe

Trailblazers: Dr Michelle Wille is a world expert on avian influenza. She is a Senior Scientist at the WHO Collaborating Centre for Reference and Research on Influenza, and recipient of the Victorian 2024 Young Tall Poppy Science Award and 2024 Australian Biosecurity Award. She was desperately worried about a pandemic in 2020, but it wasn’t covid.

We are in the middle of a pandemic. It’s an animal pandemic, a panzootic, caused by a strain of influenza called H5N1. It has been catastrophic for wildlife, catastrophic for the poultry industry, and it’s had very big impacts on other industries, like dairy in the US. It’s also causing human infections.

H5N1 is present on every single continent on Earth except Oceania – that means Australia, New Zealand and the Pacific Islands are the only places in the world this virus isn’t found. Yet.

Everywhere it goes, avian influenza causes mass mortalities – dead birds and mammals – so there are very big conservation concerns.

I’ve been working on avian influenza my whole career. My current role is at the WHO Collaborating Centre for Influenza in Melbourne.

Here in Australia, I co-run a surveillance program. We go out into the field, catch birds, and try to understand which viruses they have. We’re also doing early-warning surveillance; each spring, we travel across Australia to catch as many birds as we can as they’re arriving from their migrations to ensure that they haven’t brought H5N1 with them. We also do research through trying to take the surveillance information and contextualise it to generate answers that are helpful to our colleagues in government who need to understand and respond.

By using the genome sequence data that we can generate from avian influenza, we can understand more about their mutations, their spread, and their impact on populations.

Avian influenza isn’t one thing. It’s actually a collection of a large diversity of different strains and subtypes.

Avian influenza are strains of influenza A found in birds, but influenza A can also infect humans and other animals.

Within avian influenza, we can categorize the viruses in two ways. The first way is through subtypes of the HA and NA proteins found on the outside of the virus. There are 17 HA different subtypes, and 9 NA subtypes found in birds. These subtypes mix and match, and we report them in combination. So H5N1 means it’s type five of the HA and type one of the NA.

If you read the news, you’d know that here in Australia we’re seeing H7N9, H7N8 and H7N3 – all different subtypes which are genetically different.

The other way we classify the viruses is based on pathogenicity. The vast majority of avian influenza viruses don’t cause any disease at all; they’re just part of the natural collection of microbes that are found in wild birds, specifically wild waterfowl. These are referred to as “low pathogenicity viruses”. But when H5 or H7 of these low pathogenicity forms gets into poultry, particularly chickens, they can evolve to become highly virulent strains. And that’s exactly what’s happened in Australia: low-pathogenicity H7 viruses, found naturally in wild birds, jumped into poultry farms in Victoria and NSW, and evolved into these “high pathogenicity”, virulent viruses, and those viruses then spread between the poultry farms. High pathogenicity means it kills birds, and more than two million chickens have died or been culled in Australia in the past year due to these viruses.

But that’s different from H5N1. That’s a virus that jumped from wild birds into poultry in 1996, became high pathogenicity, and retained that phenotype for decades. Between 1996 and about 2014, H5N1 was really only found in poultry in Asia.

In 2014 we started seeing it jump into wild birds from time to time, but it tended to kill the wild birds, so they couldn’t spread it very effectively. But there was a change in the virus in 2020-21 that changed the game.

Wild birds, particularly waterfowl like ducks, didn’t necessarily die from avian influenza, and because not all of the ducks weren’t dying from it anymore, they could transmit the virus long distances.

I distinctly remember seeing a really big increase in notifications to the World Organisation of Animal Health in early 2020 and being really worried about it. Then we started seeing a massive explosion, and it travelled the world from there.

The virus arrived in the sub-Antarctic in about October 2023 and it was first detected in the Antarctic in February 2024. If we look at what’s happened in other places, particularly South America, the impact has been catastrophic: more than 500,000 wild birds in South America have died. And those are only the carcasses that we have counted. About 40 percent of Peruvian pelicans in Peru died in less than a few months.

Given these big impacts elsewhere, we are very worried about the Antarctic because there’s a lot of endemic species only found there, and many of them are colony-nesting, so they live in big groups. An infectious disease going into a big aggregation has the potential to have a really devastating impact.

It’s very tricky to study this virus in Antarctica, because we don’t have a lot of people living there who can report mass mortality events, so the data we’re collecting is quite patchy. It has seemed to mostly be transmitted by skuas, which are like a brown seagull. They’re predators and scavengers, and every time H5N1 is found in a new location, it’s always first found in these skuas.

So far we haven’t seen mass mortalities of penguins, which is quite a relief, but colleagues have recently found it in penguins that are still alive, so we are definitely trying to understand what’s going on.

This avian virus has been found in at least 50 or 60 species of mammals, but for most species it’s quite self-limiting; we’re seeing it in bears, foxes, minks – all kinds of mammals that are predatory or scavenging and eating infected birds.

The exception are some marine mammals, particularly in South America. More than 20,000 South American sea lions have died from this, but we can only count the ones that die on land. Colleagues of mine in Argentina went to what would have been a breeding colony of southern elephant seals and extrapolated that 18,000 one-to-two-week-old pups had died, so that’s an entire year’s breeding effort.

It’s very, very distressing. I’ve been passionate about nature since I’ve been very young: my dad used to take me birdwatching to give my mum a break when I was a baby, so I’ve been a keen birdwatcher most of my life. Now I sit in these meetings with colleagues who want to do something but don’t know what to do. It has been awful. You can sometimes feel quite helpless.

The encouraging thing is that we’re working together. We’re doing what we can. We have a lot more systems in place now to respond. We’re trying to look for solutions, but it’s very challenging.

As told to Graem Sims

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