When Victorian health officials confirmed Australia's first human case of avian influenza last week, there were a few key details that struck some of those listening as odd.
The announcement came on the same day that the state's agriculture department reported an outbreak of bird flu at a poultry farm near Meredith. But the Department of Health made clear that the two incidents were totally unrelated.
In fact, the human case, a two-year-old who had recently returned from India, had been detected in early March. One of Australia's leading epidemiologists, Professor Raina MacIntyre, noted the almost three-month delay in reporting the case was "not ideal".
The source of the human infection was also somewhat mysterious. Health officials confirmed the child had picked up the highly pathogenic virus while travelling in India, but did not note any close contact with sick animals or other infected humans.
Two further outbreaks on Australian poultry farms followed, prompting hundreds of thousands of chickens to be culled, while deadly strains of bird flu continued to wreak havoc on the US dairy industry and wild animal populations around the world.
There is an unsettling, familiar tone to all of this news, and a quiet hum of concern runs beneath it — could avian influenza erupt into the next pandemic?
Some of the world's foremost experts in infectious disease and public health governance say while it is not time to panic, there is a reasonable risk that we must be prepared for.
"What we worry about is those avian viruses mutating to pick up an adaptation to the human respiratory tract. That's how a human pandemic would emerge," Professor MacIntyre said.
These experts share a concern that the fatigue and divisiveness wrought out by the COVID-19 pandemic present significant challenges in tackling new outbreaks head on — already they are hampering efforts to test, report and contain the outbreak in the US.
They also believe we're closer to another pandemic than many people realise — but we have "a golden opportunity" to prepare now and get it right.
What's going on with bird flu in Australia?
First, it's helpful to understand how different outbreaks of bird flu are categorised.
Avian influenza is an infectious disease that spreads predominantly among wild birds and poultry. Just like human influenza, there are several types of avian influenza viruses — these are classed broadly as either high pathogenic or low pathogenic, indicating how sick they make infected birds.
As with other infectious diseases like COVID-19, avian influenza viruses are divided into subtypes or "strains" and then further into clades. These subtle differences occur as the virus evolves and mutates to work around host cells' defences. Some adaptations can lead to "spillover" events, where the virus passes from one species to another to infect other animals and, in rarer cases, humans.
Australia has dealt with a handful of highly pathogenic avian influenza outbreaks in recent years, but until now, none of those involved human cases.
Last week, Agriculture Victoria disclosed an outbreak of H7N3, a highly pathogenic strain of avian influenza, at a poultry farm near Meredith.
Later that day, Victorian health officials confirmed Australia's first human case of avian influenza, the child who picked up an infection in India — a different strain known as H5N1.
On May 24, a second avian outbreak was confirmed at another Victorian poultry farm in Terang, which had commercial links with the farm in Meredith. Testing confirmed this outbreak was another H7 strain, known as H7N9.
A third outbreak was confirmed last week at a mixed poultry farm in Western Australia – a low pathogenic H9N2 strain not connected to the Victorian outbreaks.
State and federal authorities are working with affected industries to control the poultry outbreaks, with the infected farms under quarantine and orders for free-range and backyard flocks within restricted areas to be temporarily housed.
It's important to note that the human case is not connected to the outbreaks at the poultry farms, and contact tracing has identified no further human cases in Australia at this stage.
GISAID, a global database tracking infectious diseases as they evolve, identifies the human case in Victoria as H5N1 clade 2.3.2.1a. Genomic sequencing shows this is connected to the virus that is currently circulating in India and Bangladesh.
Another H5N1 clade, 2.3.4.4b, has been wreaking havoc across North America, Europe, and parts of Africa and South America.
In the US, it's at the centre of the longest and largest bird flu outbreak in history, causing the deaths of more than 90 million birds. It has also been detected in dairy herds across nine US states, prompting a swathe of restrictions and control orders to stem the spread. Three human cases have been linked to the US dairy outbreak.
H5N1 and other strains are also circulating in China. A woman from Fujian province died in April after falling ill with the highly pathogenic H5N6. According to the World Health Organization (WHO), she had been in contact with backyard poultry before she became ill.
What's the risk of human transmission?
The risk of human transmission of avian flu viruses is relatively low – it's generally picked up where there has been close contact with infected animals. Health authorities around the world are urging caution among people working in affected industries such as poultry and dairy, or other jobs handling wild animals, but overall, the risk to the general public is considered low.
Professor MacIntyre, who leads the global biosecurity program at the Kirby Institute at University of New South Wales, says this is due to the way this virus operates.
"Avian flu viruses are adaptive to birds, and birds have specific receptors in their upper respiratory tract that we do not have. Those viruses only spread easily between birds and between some mammals — not humans," she said.
But that could change if the virus has opportunities to pick up adaptations that allow it to enter the human respiratory tract.
Professor MacIntyre notes that avian influenza has already crossed over from animals that have traditionally carried the virus — waterfowl including ducks, geese and swans — into other wild birds and even mammals.
"We've seen mass die-off of sea lions and seals, red foxes, coyotes, squirrels … and we're now seeing it in 130 other wild birds that were never hosts for spreading this virus before," she said.
In South America, hundreds of thousands of sea birds have died including more than 40 per cent of Peruvian pelicans. Scores of Adelie penguins and skuas have died in "mass mortality events" across Antarctica, with H5N1 the suspected cause.
"Antarctica is a worry for us," Professor MacIntyre says, "because if the virus is in Antarctica, then there could be flyaways of other birds that could bring it into Australia".
Professor MacIntyre says the statistical probability of the virus adapting to infect humans more efficiently is highest with the H5N1 clade 2.3.4.4b. If this kind of mutation were to occur, she suspects it would be in Europe or the Americas.
In the United States, the Food and Drug Administration (FDA) has found fragments of the H5N1 virus in samples of milk and other dairy products for sale in grocery stores. However, none of these samples returned evidence of live virus. This is likely down to the pasteurisation process, which Professor MacIntyre explains "kills the virus".
In Australia, food standards require most milk or milk products being sold commercially to meet pasteurisation requirements. Unpasteurised or raw milk — apart from goats' milk — is restricted from being sold as a food product, though there are exceptions in some states that allow local producers to sell raw milk cheese under strict circumstances.
The raw milk market appears to be growing in the US, and while the FDA has warned consumers to avoid these products given the current H5N1 outbreaks, Professor MacIntyre says this is where she has concerns.
"[If] people are drinking raw milk, that's where you're going to possibly have the avian virus mixing with humans and creating more chances for that mutation," she said.
While there have been no human cases related to food consumption, the CDC reported that cats at a Texas dairy farm became sick after being fed raw milk from infected cows. According to the report, more than half of the cats died.
For the moment, the World Health Organization, as well as centres for disease prevention and control in Europe, the US and Australia, doesn't appear to be alarmed about the risk of a wider outbreak or pandemic affecting humans. In its latest weekly update, the WHO wrote:
"Whenever avian influenza viruses are circulating in poultry, there is a risk for sporadic infection and small clusters of human cases due to exposure to infected poultry or contaminated environments … The zoonotic threat remains elevated due to the spread of the viruses among birds. However, the overall pandemic risk associated with A(H5) is considered not significantly changed in comparison to previous years."
Amesh Adalja, an infectious disease doctor and scholar at the Johns Hopkins Center for Health Security, notes that the CDC's Influenza Risk Assessment tool has ranked H3N2 and H7N9 as the most threatening in terms of avian flu strains. But he says it's important to keep an eye on how the H5N1 clade 2.3.4.4b evolves.
"[We would be looking out for] mutations, as well as reassortment with human or swine viruses. The fact that it's infecting mammalian species — that's one of the major hurdles a flu virus has to clear for efficient human transmission. There's been some mild mammalian adaptation here and there, but not enough to change the public health threat," he said.
However, as several public health and infectious disease experts have warned in the past few years, the question of another pandemic is not so much a matter of if, but when.
Are we prepared for the next pandemic?
Professor Kelley Lee has been studying the governance of global pandemics for years, and most recently her work with the Pandemics & Borders international research group has been reflecting on the response to the COVID-19 pandemic and strengthen strategies for future outbreaks.
Broadly, her work aims to answer the question: is the world prepared for another pandemic?
"I would say the short answer is no, we're not anywhere near prepared. And indeed, in some ways, I think we're worse prepared than we were prior to COVID-19," she said.
Professor Lee says the biggest lesson from the COVID-19 pandemic has been how global collaboration was instrumental in managing the spread and science the virus — from identifying SARS-CoV-2 as a novel pathogen, to developing vaccines and potential drug treatments.
And conversely, where coordination was lacking, it slowed down the world's ability to bring the virus under control. One example was the varied approaches to imposing travel restrictions and border controls, which her research has shown came at huge economic and societal cost.
"When you have an uncoordinated introduction of policies, where every country did things differently and would change them over time … it's nothing short of chaotic," she said. "It's costly, but it's also not a good way of managing risk."
Professor Lee says jockeying between countries and their citizens over access to resources, "vaccine nationalism" and other behaviours such as people hoarding ventilators and masks, did significant damage. "Populations that really needed those essential supplies didn't get them in time or didn't get them at all," she says.
Over time she believes this contributed to a pervasive corrosion in trust and social cohesion.
"We're more divided than we were before COVID. You would think that a generational event such as this would have brought us closer together … but in general, societies are more fragmented, less cohesive, and less trusting. That kind of social environment makes us far less likely to cooperate or coordinate our efforts, from the local level all the way up to the global level."
Professor Lee says she's seeing this play out in the ongoing Global Pandemic Accord Negotiations, which this week failed to finalise a draft agreement after more than two years of discussion.
Dr Adalja, who has been advising public health bodies in the US during the recent H5N1 outbreaks, says a similar dynamic is frustrating efforts to manage the virus there.
He says there has been a lack of transparency around testing, and in many cases a lack of access for public health authorities. The setting of this outbreak – in dairy farms across a dozen or so states – adds a layer of bureaucracy that has further complicated the process. At times, public health officials from the CDC haven't been in sync with the Department of Agriculture, or with the state governments which must grant access for federal health officials to carry out testing on farms.
"We saw with swine flu in 2009, there was reticence to really address the risk on farms, and to sample farms — this has gotten better, but we always run into this because there is a very big commercial aspect in terms of export, and domestic consumption of meat and milk," he said.
"So these types of things are constraining the ability to do more widespread testing, to get more important public health information out, at least to the farm workers where we think this risk is really high."
On top of that, Dr Adalja notes that the stigma associated with testing for a highly pathogenic avian influenza carries a huge economic risk — Colombia has already restricted imports of beef from US states where dairy cows have tested positive, and Japan and the US have made similar moves to suspend Victorian poultry imports. But this matters on a micro level, too.
"Many of the people that work on these farms are migrant workers. They may not be willing to be tested because if they're sick, or if they're found to be positive, they won't be able to work, which means they won't get paid," he said.
Dr Adalja is concerned that if we don't get the response right this time, it doesn't bode well for any future pandemic scenario.
"The problems we're seeing now are not a good indicator of how well we would handle a more serious bird flu. It's important to get this ironed out, because it's likely going to involve agriculture of some sort, whether that's poultry, cattle, or swine, so we need to have really robust surveillance of what's going on there."
So what can be done?
Professor MacIntyre says for Australian authorities working to contain the current poultry outbreaks, the most urgent priority should be considering financial measures to make robust testing and reporting as straightforward as possible.
"The biggest thing that can be done is financial compensation for farmers. Without that, there's not going to as much testing and reporting as there should be, and outbreaks won't be disclosed," she said.
Dr Adalja is similarly focused on managing the outbreaks in livestock industries well. He says a lack of trust in public health officials is a fundamental issue to solve for efficient and thorough testing and surveillance. Involving veterinarians with established relationships in the industry is among some of the suggestions to work around this.
Outside of encouraging stringent testing in these industries, Professor MacIntyre says the other sign to watch out for will be mass die-offs of birds or other wild animals.
And while the current local outbreaks don't pose an immediate risk of human transmission, it's a possibility she says we need to be prepared for.
"In terms of the human pandemic, it's a problem for everybody. If a pandemic arises in the US or Europe, it's going to end up here. So it's in our interest to be closely monitoring for that."
Professor MacIntyre views global data sharing and surveillance as paramount in those efforts. Professor Lee says this extends to all facets of infectious disease management.
"We did learn that we can develop a new vaccine very quickly if we all work together … and there are a lot of scientific advances on the horizon that I think would make us more prepared," she said.
"But this is a really a population health challenge. It needs society to work together. If you have everybody hoarding toilet paper or masks or just looking out for themselves, that doesn't actually help them, because the virus continues to circulate."
Cross-border communication is also critical, Dr Adalja says, "because we know that these types of viruses don't stay in one country, especially when they're hitchhiking on birds that migrate all over the world".
And while highlighting all of these challenges may tap into a well of fear, he believes "this is a golden opportunity to get it right".
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2024-05-31 19:15:00Z
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