PODCAST: H5N1, bird flu

24 May 2024

WHO/Europe has today published its latest podcast in the 'Health in Europe' series. Episode 45 takes a deeper look at H5N1, commonly known as bird flu or avian influenza. We talk to the experts and ask: are we prepared for another pandemic in Europe? 

The podcast features: 

• Peter Sousa Hoejskov, Technical Officer for food safety and zoonotic diseases, WHO Regional Office for Europe
• Nicola Lewis, Director, Francis Crick Worldwide Centre for Influenza in London
• Aisling Vaughan, Epidemiologist, WHO High Threat Pathogens Team
• Maria van Kerkhove, WHO Acting Interim Director, Epidemic and Pandemic Preparedness and Prevention

Hosted by Alice Allan

​​​Listen here or wherever you get your podcasts: https://www.buzzsprout.com/1109867/15128389 

TRANSCRIPT FOLLOWS: 

Alice Allan: Throughout history, pandemics have swept around the world leaving devastation in their wake. What are we doing to prepare for the next one? Hello? I'm your host, Alice Allen, and in this special series of Health in Europe, I'll be going behind the scenes at WHO and some of the European region's major public health institutions to understand what the most likely causes of future pandemics could be and what strategies are in place to avert them.

I'll talk to the experts applying the lessons of previous pandemics and focus in on the systems in place to spot threats and reduce their impact. I'll speak to the legion of public health experts quietly working away, getting on with the not very glamorous but incredibly important work of emergency preparedness. Experts in surveillance, genomic sequencing, and monitoring. Epidemiology and more. The people who are containing outbreaks and laying the groundwork to mitigate the effects of pandemics, not if, but when they occur.

This is Health in Europe. And in this episode, we explore H5N1 bird flu.

Peter Sousa Hoejskov: My name is Peter Sousa Hoejskov, I work as a technical officer for food safety and zoonotic diseases in the WHO. Regional office for Europe based in in Copenhagen.

Alice Allan: Zoonotic diseases have been around forever. But while the threat has always been there, the virus behind the COVID 19 pandemic, SARS-CoV-2, which originated in bats, and more recently the jump of avian flu into cattle, has put them back in the news.

Peter Sousa Hoejskov: So zoonotic diseases are diseases that can jump from animals to humans. So basically, a disease that originates in an animal and transmits to a human. Either directly, with direct contact between animals and humans. It can be domestic animals, it can be wild animals, or it can be indirectly as well through unsafe food, for example.

Alice Allan: Here in Europe, we might think sometimes that, oh, zoonotic diseases, that's something that happens somewhere else in the world. Why are zoonotic diseases also relevant in the European region?

Peter Sousa Hoejskov: Everywhere in the world, including in the European region, there is close contacts between humans and animals. We have large agricultural productions in the European region, livestock breeding sites. We have domestic animals. We interact every now and then with wildlife. So, there is this constant interaction between humans and animals. We can't completely separate ourselves from the animal world. So, when we have this interaction, there is also a risk of transmission of diseases between animals and humans.

Alice Allan: Why are we hearing more recently about the threat of zoonotic diseases?

Peter Sousa Hoejskov: We know that the SARS CoV 2 virus, this is the virus that causes COVID 19 as a disease, originated in the animal population and then through an intermediate host ended up in the human population. And with the mutations that viruses can have, then the transmission between humans can become more serious. And that was exactly what we saw with the COVID 19 pandemic. So I think that this, of course, increases the interest and triggers the attention of where we need to be better prepared for the next potential pandemic. We don't know when it will happen, but we know it's very likely to happen. We also know that a lot of the new infectious diseases that we see in humans originate in animals.

Alice Allan: Is there anything about our modern way of life that is increasing the risk of zoonotic transmission?

Peter Sousa Hoejskov: Yes, with more urbanization, we get closer interaction with the animal population. We see climate change as an effect as well that affects how the viruses survive and how they mutate. We see changes in the agricultural practices, the way we breed animals, more intensive livestock breeding.

Alice Allan: Tell me about One Health.

Peter Sousa Hoejskov: One Health is an approach, it's a way of working, seeing these health threats and the health challenges that we are facing in a much, much more holistic and a more systematic way.

Realizing that we cannot prevent and prepare for pandemics in the human health sector alone, we need to also work across sectors, across disciplines. We need to work with colleagues and other organizations or at country level with other ministries. So, a very close collaboration, sharing of information, joint risk assessments across the veterinary services, agricultural sector, environment sector, and human health.

And that's exactly what One Health is all about. It is to see health as one across these different domains and encouraging closer interaction, closer coordination and sharing of information so we can be better prepared and act fast if we need to. We have a formalized partnership with what we call the Quadripartite Organizations. So that's the Food and Agriculture Organization of the United Nations. It's the World Organization for Animal Health, WOAH, and it's the United Nations Environment Programme, UNEP. And then WHO. So, we work very closely together. We have also developed joint guidance material for countries on how they can operationalize the One Health approach, basically, what are some of the tools, what are some of the techniques and how can they better implement and, and work across sectors at a country level because One Health is not at the global level only of organizations working together. It comes all the way down to communities and we know the next pandemic is also going to start in a community somewhere. So, we need to be better prepared at community level. So, One Health is at all levels and across various sectors and disciplines.

Alice Allan: Nicola Lewis is Director of the Worldwide Influenza Centre at the Francis Crick Institute in London. It's a WHO collaborating centre and one of its key functions is to track strains of influenza that are circulating among animals and humans to understand how it's changing.

Nicola Lewis: So, flu is fascinating and I think one of the aspects of flu that is fascinating is it's continuously evolving. It's changing the whole time. It's a virus that when it replicates in a particular host makes mistakes and it makes mistakes in its genome. And that means that it's able to constantly evolve. And some of this evolution means that it's able to escape prior immunity that we might have to a particular flu virus.

So we are really facing a challenge constantly to try and keep up with this changing evolution. Flu viruses are also fascinating because they can do something else in terms of changing constantly. They can undergo what we call reassortment. And this happens when two different flu viruses infect a person or infect a pig at the same time, and they shuffle their genetic material so that the progeny flu virus that comes out of the pig or other human is actually different.

And this process of reassortment is also a way that flu viruses evolve. Now we know that flu viruses are particularly tricky to understand from this point of view because this whole evolutionary process means that we have to stay abreast of this evolution to understand where the next threat might come from.

Alice Allan: Big scientific advances have been made in the last hundred years about understanding viruses and tracking them. How close are we to being able to keep up with flu?

Nicola Lewis: I think we're getting much, much better at trying to keep up with the evolution of these pathogens. I certainly think that new technologies are coming along all the time, and we make the most of those, particularly in the influenza field. But because flu changes constantly, it constantly presents a new challenge to us. So, just, we certainly can't drop our guard with flu viruses, and I think there is one certainty and that is that there will be another flu pandemic in the future.

Alice Allan: Can you think of a particular moment when flu has done something that has shocked or surprised you? One of those moments when you've gone, gosh, wow, flu, that was interesting.

Nicola Lewis: I think one of the major surprises has been quite recently, actually, with the H5 highly pathogenic viruses that have been circulating in bird populations. And we've been facing a massive challenge with these viruses since about 1997, but in about mid-2020, we suddenly saw a radical shift in the way that these viruses were evolving. All of a sudden, rather than being confined to particular geographic regions, they managed to switch back into wild birds. They managed to infect many more wild bird hosts and then they managed to spread globally to the extent that, since 2020, they've spread not just throughout Eurasia, not just through into Europe, into Africa, but they've also hopped over the Atlantic and have now spread right the way down North America, South America, and have just turned up in Antarctica.

We have never seen this kind of situation with a highly pathogenic H5 virus before. And I certainly think that if you'd asked me in 2019, this would not have been the picture I would have conjured up in my mind about what bird flu could do.

Alice Allan: How are scientists responding to this new behaviour?

Nicola Lewis: As researchers, we are very committed to understanding what has changed with the virus. But also, what we can do to help populations of animals and indeed the human population be prepared to be able to counteract these infections, to be able to mitigate them and to essentially prepare for a potential pandemic from these viruses. So, there are a number of different initiatives that we undertake to keep up with these viruses.

The first is to sample these viruses in animal populations, to characterize them, to sequence them, to antigenically characterize them, to understand what they look like in these animal populations, in bird populations, but also in when they've spilled over into terrestrial mammal populations around the world.

And the next part of this is to understand what these viruses look like relative to what we call candidate vaccine viruses. And these are viruses that the WHO network of global influenza surveillance response network worldwide, we take these viruses and we try to understand the similarity to potential candidate vaccine viruses we might have to use whether to be a human pandemic.

And so twice a year, the WHO collaborating centres that are part of this GISRS Global Influenza Surveillance and Response Network come together twice a year. And we have a very important job to do twice a year. One is to make recommendation for seasonal influenza viruses, for the vaccine strains. But the other is to look at the viruses that are circulating in animal populations and to think about what we need to prepare for, what kind of candidate vaccine viruses we might need to have in our armoury to help us where there to be a pandemic tomorrow.

Alice Allan: In the European region, detections of H5N1 have been made in farmed fur animals in Finland and Spain, and also in domestic cats in Poland. Aisling Vaughan is an epidemiologist WHO Europe in the High Threat Pathogens team. I started by asking her what the team had learned from working on these outbreaks.

Aisling Vaughan: I think what we learned from these events in, um, Europe most recently was that a strong foundation of trust amongst stakeholders is really, really important. It enables rapid information exchange. It allows for coordinated multi sectoral efforts, and it really drives decisive actions to effectively prevent any further viral spread and then of course, safeguard both human and animal health.

Alice Allan: How do you assess the current risk of H5N1 to humans, particularly in the light of the recent detections in cattle in the US?

Aisling Vaughan: So, it's important to remember that this virus mostly affects, wild birds and domestic birds. It rarely affects humans. And there's really no evidence yet that this virus has acquired the ability to spread well from person to person, and despite the high number of clades 2344b outbreaks we've seen and the detections and animals and as well the human exposures to this virus at the human animal interface, relatively few infections have actually been reported to date, which is reassuring.

So, overall, since the beginning of 2021, 28 detections of H5N1 in humans have been reported to WHO, including the most recent case who had exposure to dairy cattle. So, of all of the H5N1 cases reported in Europe and North America, they have been asymptomatic or mild. So, for example, the most recent case in the US reported conjunctivitis as their only symptom. All H5N1 cases, so far have been sporadic infections. They've occurred through direct or indirect contact with infected birds or infected mammals, or environments such as live poultry markets or other premises with infected animals. And among these cases, there have been no reported human to human transmission, and in fact, there have been no reported human to human transmission of H5N1 since 2007.

So based on everything we know, based on all the information available, WHO assesses the current overall public health risk posed by H5N1 to be low. And for those with exposure to infected birds or animals or contaminated environments, the risk of infection is considered low to moderate. But these viruses are continually evolving and spreading in birds and animals so continuous real time monitoring is needed.

Maria van Kerkhove: I think with almost certainty we will have another flu pandemic in our lifetime.

Alice Allan: Dr Maria Van Kerkhove is the acting interim director of the WHO's Department of Epidemic and Pandemic Preparedness and Prevention. She also leads on COVID 19 emergency management and she's technical lead of the WHO Health Emergencies Programme.

She started her career working on avian influenza 20 years ago.

Maria van Kerkhove: I became interested in viruses, pathogens when I was in college, and when I was doing my PhD at London School of Hygiene and Tropical Medicine. And as part of my PhD work, I was based in Cambodia and I was working with Institute Pasteur, Cambodia on H5N1 and avian influenza.

And at the time there were six or seven human cases in Cambodia, so it was relatively new. And what we were doing there with colleagues across the Ministry of Health, the Ministry of Agriculture, Institute Pasteur, we were doing these outbreak investigations. And I was fascinated with outbreak investigation.

It was multidisciplinary. It was all One Health before it was even called One Health, you know, and it was really just early detection and early action to prevent onward spread. So we were doing all these complex, comprehensive investigations in the field. Oh my gosh, I absolutely loved it.

Alice Allan: Why are we hearing so much about H5N1 recently?

Maria van Kerkhove: So, there's a lot of attention right now to avian influenza and there's a massive epizootic across the world. Um, it has expanded greatly in the last couple of years. This is particular on H5N1, but not only H5N1. We see in wild birds, we see in domestic, poultry, we see in spillover into mammals, including humans, but this is being detected in, in, in new countries. Right now, there's been quite a lot of attention on H5N1 in dairy cows, in dairy cattle in the U. S., and, you know, it is unfortunate that the world starts to pay attention when you see this in high income countries, but we will use this attention to draw awareness to, one, the global influenza and surveillance response system that's been in place for 70 years.

WHO did not wake up to flu. We've been working on this for quite a long time because we know there's seasonal influenza, there's a potential for pandemic influenza, and there's all these novel subtypes of avian influenza. And we work with the PIP framework of looking at how do we have better capacities in countries for these types of detection, but also how do we share viruses with our global lab network, our national influenza centres, our WHO collaborating centres to identify certain viruses that should be thought of for vaccines.

Alice Allan: The PIP framework is WHO's pandemic influenza preparedness framework.

Maria van Kerkhove: So, we have these candidate vaccine viruses, including many H5N1 vaccines, which, which prompt us already to have H5N1 vaccines in development.

Now, I do want to contextualize this that since 2017, we've only had 28 human cases of avian influenza. We have not seen human to human transmission. We're constantly looking, because our worry is that these viruses can be more adapted for transmission. We have not seen that yet, but we are concerned the more opportunity this virus has to circulate, the more opportunities we see for infection in different species and these viruses can combine, the genetic components of it can combine, and potentially cause a new virus of influenza that could be highly transmissible. That's what happened in 2009. So, we're constantly thinking about this, not just thinking, but taking action to be better prepared.

What we want to do is prevent, prevent, prevent. There are some treatments for influenza. We have vaccination. So, there's a seasonal vaccine campaign every year. We urge people to get not only COVID vaccines, but also influenza vaccines. And there are H5N1 vaccines in development, should we need them.

Alice Allan: This recent species jump into cattle, what's WHO, or what are your partner agencies doing to understand development and any potential risks to humans?

Maria van Kerkhove: Yeah, quite a quite a bit actually. So, what we're trying to do is enhance the surveillance not because we have a global surveillance system in humans as part of our GISRS system, which is looking at sentinel sites, so patients that are going into hospitals, some are non-hospital sites. We're working with FAO and WOAH on surveillance in animals. So, in wild birds, in poultry, in livestock, and now that we're seeing infections in certain species, we want to make sure that those species are tested more systematically. So not just dairy cattle in the U.S., but we would ask more globally for surveillance to include these animals, but not only in the animals themselves, but looking in the products of those animals like milk and milk products. So, there's a lot of work that has to happen there to understand the extent of circulation. We advise that, sequencing be conducted and shared because there's a lot that we can gain in our understanding of transmission and circulation of with the sequence information. So, I don't have the full picture, but that's just because the work is ongoing as we are talking about this right now. We also are very actively engaging with our WHO collaborating centres, national influenza centres, to make sure that samples that need to be in the right labs to do the right types of laboratory research type studies are ongoing, and that information is shared. And we're constantly doing risk assessments.

Alice Allan: What kind of key factors could contribute to a species jump to humans for H5N1?

Maria van Kerkhove: So, one is opportunity, right? So as these species intermix with each other, you know, we have wild birds that are flying, and so there's opportunities for the virus to spread between poultry and other species, wild birds and other species. And that's what we think has happened here based on the sequencing information. We're also very carefully looking at the viruses. And looking at the mutations within the viruses, any changes that would favour its mammalian adaptations, that’s what they call it, would favour a transmission in mammals.

Now we're seeing some changes, but these are mainly primarily poultry viruses and they have not adapted well to transmit between people and in mammals. And that's a really important thing that we're tracking. We have a lot of really fantastic…I mean, I mean this with the utmost respect, super nerdy scientists who I adore around the world who are looking at this with us.

So, it's not just WHO sitting here saying, what do we think? What we do is we bring together the best minds in the world as part of our global influenza surveillance and response system. We do this for COVID as well. And for SARS-CoV-2, of what do these changes in the viruses mean from a public health point of view? So that is something that's also ongoing.

Alice Allan: There have been a lot of headlines recently predicting that the next pandemic is going to be caused by an influenza virus that's jumped from animals to humans. How do you assess that risk?

Maria van Kerkhove: For me, flu is a certainty, um, because it's so much in circulation. It's infected many different species. We have avian influenza and the opportunities for reassortance, the opportunities for a pandemic. influenza virus are high. That's why we have a whole system in place to be prepared for this. The challenge is, will we see another coronavirus pandemic? Given that we had SARS-CoV-2 cause a pandemic, for sure, this is an opportunity. The question is, will we see an Arbovirus pandemic? Now, I'm not saying this to scare people who are listening to this, but for us, it's something that we have to be prepared for. So, we have to think out of the box. You know, really prepare for what are the known threats, but also think out of the box, you know, for something different, perhaps waterborne or whatnot. So for me, pandemics, unfortunately, are part of what we will deal with in our lifetimes. I don't believe this will be the last pandemic we will deal with in our lifetimes.

Alice Allan: We know we weren't prepared for the COVID 19 pandemic. Are we prepared for the next one?

Maria van Kerkhove: Yes and no. Yes, because we do have strong systems that are in place. We have learned a lot in the last four years from COVID. We have strengthened PCR capacity, sequencing capacity, we have stronger community engagement. We have many systems that are in place to ensure better clinical care and infection prevention and control and good coordination in our emergency operation centres and supply chain.

No, on the other hand, no, because I think the world's trust in science, you know, there's been a lot of distrust over the last couple of years. And that's something we have to work on. You can develop the best interventions in the world, but if they're not implemented by communities, they're useless.

We still have challenges with equity and access to these materials. And I think, you know, in many respects we are better off and in others, we are not. I'm optimistic. That's what gets me out of bed every day. Otherwise, I wouldn't be able to do this job. I'm hopeful with the pandemic agreement that is being discussed and negotiated right now by all of our member states.

And, and what I hear, you know, is they want to get this done. They want to get this done because we can't just have a handshake and say, ‘Oh, we'll do better next time’. There have to be commitments in place to ensure that we do better the next time. Again, COVID-19 did not have to be as bad, um, as it was, as it is and we owe it to our children, our grandchildren to make sure that we, we keep up these systems and have that commitment in place to make sure that we do better the next time.

Alice Allan: In future episodes, I'll talk to experts who are tracking disease outbreaks, trying to understand them better and preparing for future pandemics, not if, but when they happen.

Health in Europe is produced by the World Health Organization. Music for this episode is by Ben Howells, Richard Duttnell and Gareth Thomas. Sound engineering is by David Barrett. My name's Alice Allan. Thanks for listening.

ENDS

Media contacts: 

Bhanu Bhatnagar, bbhatnagar@who.int 

Press Office, eupress@who.int