When not if: Preparing for the next pandemic

We speak to experts on learning from the past to fight diseases of the future...
10 October 2023
Presented by Chris Smith
Production by Rhys James.


A graphic showing a face mid-cough and some virus particles.


Medical professionals largely agree: the world is far more susceptible to a Covid level crisis than it ever has been. Mass urbanisation, political instability and climate change are among the factors contributing to an increased risk of diseases jumping from animals into people. We hear from scientists who demand action before the next coronavirus arises, likely to be within the decade...

In this episode

A moon rising over a cityscape

00:40 - Virus hotspots becoming more prevelant

The factors behind an increased risk in pandemics...

Virus hotspots becoming more prevelant
Peter Hotez, Baylor College of Medicine

The deaths, lockdowns and school closures that accompanied the global spread of Covid 19 may not seem all that very long ago, but top health officials are already busy preparing for what's going to come next. Many researchers believe that another pandemic could soon be upon us - before the end of this decade, in fact. So what can we expect and what efforts are already being made to tackle the emergence of a deadly new agent? Peter Hotez is professor of paediatrics and molecular virology and microbiology at Baylor College of Medicine. He's also the author of 'Preventing the Next Pandemic. Vaccine Diplomacy in a Time of Anti-Science.' I asked him what the next pandemic might look like...

Peter - This is, I believe, the start of a new normal. Covid-19 is the third major coronavirus epidemic we've had just in the last 20 years; we had SARS that arose out of Southern China in 2002, then we had Middle Eastern respiratory syndrome in 2012. That's why we started working on coronavirus vaccines, because we knew a third one was around the corner. And, sure enough, right on cue came Covid-19. And by that same reasoning, we should expect a fourth major coronavirus epidemic/pandemic before the end of this decade - every six, seven years. That's next. I'm still very concerned about the zoonotic influenzas (avian or other) that's on the radar, and other respiratory viruses. And, very importantly, what we're seeing now in the southern United States and in southern Europe is the rise of insect borne infectious diseases. I think it's quite a constellation of serious respiratory illnesses together with diseases transmitted from animals (in some cases there's overlap) and now insect transmitted infectious agents.

Chris - What do you think is contributing to that intensification? You're making the point that this appears to be happening with greater frequency and you're saying it's the new normal. Why do you think that is?

Peter - From what I can see, it's climate change acting in concert with other key social determinants including political instability as well as aggressive urbanisation, deforestation and poverty. Let's take the Middle East where, because of the violence and political instability there, you first of all see a halting of immunisation programmes, but that's not the only thing that's going on. You have unprecedented temperatures of 50 degrees Celsius or more causing people to flee into larger and larger urban areas such as Aleppo and Damascus, which outstrips the ability of the urban infrastructure to maintain safe and sanitary environments. And so you start seeing diarrheal disease and respiratory disease and then you stop your vector control programme so you're not controlling the Sandfly. So there's massive outbreaks of a disease called cutaneous leishmaniasis. So the Middle East is a good flashpoint area to identify how all of these 21st century forces are combining.

Chris - If we can distil it down to a sort of formula of where the hotspots are likely to be, does that mean we've got some areas we should have our eye on around the world where these new infections could be forged? They are those crucibles that you are talking about?

Peter - I think so. Certainly, those areas where we can identify the confluence of those forces. I think one of the hard parts of this is we don't have a very productive dialogue between the biomedical scientists together with the social scientists and the earth scientists. And we need better cooperation between those groups because, if you're a biomedical scientist, you're not typically talking to urban planners and economists and political scientists and sociologists to understand how those 21st century forces are working, or you're not really talking to climate scientists like we should. So we need to be getting the various academic disciplines to start engaging in an uncomfortable dialogue. And I call it uncomfortable because the way things work in academia too often is we're silent and we're encouraged to write and speak for each other and advance our careers on that basis. We need to have better crosstalk between the disciplines because that's how these infectious pathogens are working.

Chris - Where do most of these emerging infections come from? What's the actual origin because a virus or a bacterium can't just pop into existence from nowhere. So what's the root from wherever they are into people? How do they appear in the first place?

Peter - It's hard to make a general point but one of the observations is that many of these new viruses or other pathogens are what are called zoonosis, meaning that they originate in animals. For instance, Ebola, nepovirus, coronaviruses, they all circulate in bats. And so as humans come into closer contact with bats, either because of altered climate patterns which are causing the bats to undergo new migration patterns or humans are through deforestation, urbanisation coming closer into contact with them, often through a second intermediate animal host whether it's livestock or other animals, that seems to be an important driver.

Chris - So as we see human population increase, we see urbanisation increase, we're going to get more of the sorts of conflicts between us and the natural world that means potentially we're going to see more of these jumps.

Peter - That's right. In the last few years, for the first time, more humans live in urbanised environments than in rural environments. And so I think urbanisation is a huge one, particularly when it's accompanied by political instability in those climate vulnerable areas.

Chris - Based on what you've been saying, we actually clearly do understand quite a lot about what causes pandemics to emerge, the risk factors for making it more likely and where they come from. So does this mean then that, in fact, we are quite well positioned if we implement that knowledge the right way to prevent the next pandemic?

Peter - We understand it in broad strokes as we've been speaking, but when it comes to actually uncovering it at a very granular level, how an epidemic begins, we still stumble. More often than not, we don't really understand that. We know, for instance, that Covid-19 began in wet markets in and around Wuhan, but we don't exactly understand it at a granular level because we've never really done that outbreak investigation to detail it at the level that we really need. That's where the emphasis needs to be to be able to create interdisciplinary teams, which include zoologists, ecologists, virologists and immunologists, to go into areas where we think either outbreaks have occurred or where they're about to occur and do that detailed sampling. That's what we're still missing. And now, with international cooperation challenges, it's getting harder and harder to do that.

Covid-19 blood test sample

08:08 - Learning the lessons from Covid

Nipping the anti-science movement in the bud...

Learning the lessons from Covid
Michael Osterholm, University of Minnesota

So, what - if anything - can we learn from our handling of the Covid-19 pandemic? I’ve been speaking to Michael Osterholm, the director of the Center for Infectious Disease Research and Policy at the University of Minnesota. Michael has advised President Joe Biden on Covid-19 and has argued that we need to ‘learn the critical lesson of humility’ from the coronavirus pandemic. Chris Smith began by asking him to explain what that means...

Michael - As much as we as scientists want to believe that we fully understand what is happening around us from a scientific standpoint, and that in fact we have the tools to make accurate predictions about what will happen, that's just not the case. And I think this virus has laid that open in a very public way. For example, how many people even anticipated that this pandemic might last three years as opposed to just a few months? Or what might happen with immunity, either that from infection or from a vaccine. And so it doesn't mean you can't make conclusions or draw conclusions from what you know, but you always need to do it with a great deal of humility, saying, this is what I know now, but I don't know what this will mean in the weeks and months ahead.

Chris - Do you think that people lack humility about it then? Because many countries are holding Covid inquiries. In the UK, just this week, we've launched our Module 2, looking at the early responses that went on during Covid here in the UK. People do seem to be in receptive learning mode in the aftermath.

Michael - I think this is critical right now: to go back and do the kinds of reviews that are happening in the UK. I wish they were happening here in the United States. It's not because we're trying to point fingers or lay blame or find people to whom we can attribute accolades. Rather, it's all about what will we be like in terms of preparedness for future pandemics. This is not the last pandemic, and future pandemics could be much worse. If this were a 1918 like pandemic, the number of deaths would've been at least four to five fold higher. When we look at the possibility of another coronavirus infection causing the pandemic (we've already had two viruses, SARS and MERS, which appeared in 2003, 2012) and fortunately those viruses were not very infectious relative to the current coronavirus, but they killed anywhere from 15 to 35% of the people that got infected as opposed to today, less than 1%. There's nothing to say that in the future, the ability to be transmitted and the ability to cause severe illness and death won't match up together. And so we need to be better prepared for future pandemics. And the one way we can learn about how to do that is, what are the lessons learned from this pandemic?

Chris - Is there not, though, a disconnect between what the politicians want, what they're prepared to spend money on, and what the scientists, the epidemiologists, the public health fraternity, are advocating for? Because, just looking at my lecture notes that I delivered for the medical students at the University of Cambridge back in 2007, a lot of what I said about emerging infections in those lectures I gave came true. And I wasn't the only one saying it. Many, many people were trying to say to the government, we need better preparedness. But they weren't listening because they were largely, I think, looking at this statistically and saying, "Well, look, pandemics happen roughly every 30 or 40 years. What's the chances of this happening in my political cycle when voting for me counts?" Much lower. So I'm going to put that to one side. Do you not think that's a problem?

Michael - I think it is a problem and I think you've really put your finger on it. First of all, we have to understand that the potential for future pandemics to occur more frequently is very real. We have 8 billion people on the face of the Earth. Roughly one out of every eight people who's ever lived is now on the face of the earth. We need food to feed that population, which means we have a very different world full of food production animals, using bush meat from the jungles and the forests of the world and so forth. And so there's just a much greater likelihood of a crossover of a virus from the animal world or other humans to causing a future pandemic. And I think that those will still continue to be largely influenza and coronaviruses which will do that. We could have another pandemic 5, 6, 7 years from now and maybe earlier. So it's not 40 years off. I think the second thing is we do have to help people understand why we need to invest. And if you look at the economic cost of this pandemic, forget about the painful number of illnesses and deaths that we saw, just look at it as an economic impact: investing in preparedness is a very cost effective thing to do. And I think the final point to make on that is that we do make these decisions all the time in other ways. For example, one of the most well-funded fire departments in our state of Minnesota here in the United States is at the Minneapolis St. Paul International Airport. And since the conception of the airport, we have not had one major plane crash on the actual reservation at the airport. And yet we would not run that airport for a moment without that extensive fire department because they need to be there and ready to go should a plane crash. In a way, that's what we're like right now. We can tell you that at any moment another pandemic plane could crash and we need to be prepared for that, just like we support fire departments in settings like our airports, we need to be supporting public healthcare preparedness in ways that we have not yet really understood.

Chris - What should the shape of that preparedness be? There's going to be an international preparedness and a domestic preparedness, and that may differ a bit around the world, obviously, but what's the broad shape of that?

Michael - Well, the first thing that we have to understand is what really can make a difference in a pandemic. I've just finished a new book coming out this next year on lessons learned and one of the things that I review in some length are the non-pharmaceutical interventions, the idea of lockdowns, the idea of mandatory testing or mandatory vaccination, the idea of what we do with schools and so forth. And I think there's a lot to be learned there about what didn't work. I was never a supporter of the classic concept of lockdowns because, early in the pandemic, I made the prediction that this could easily last three years or more. And in the case of the United States, I predicted we could have over 800,000 deaths in March of 2020. Not a popular statement at the time. And, in fact, lockdowns are the idea of temporarily keeping you from the virus and the virus from you. But it doesn't at all apply if we're going to do this for three years. People can temporarily shelter in place and reduce their contact, but for three years? Remember, this is a zero sum game in the end.

Chris - That's effectively the game that China have tried to play and it doesn't work.

Michael - Exactly. Within two months after relaxing their stringent requirements, they had 120 million new deaths occurring in China from this. So it's exactly that. And so my whole point has been, this doesn't mean we don't try to flatten the curve, which is a different concept where healthcare facilities are being overrun with numbers of patients. Can we slow down transmission? So instead of having a thousand new patients this week, we have a thousand new patients over the next two months, that type of thing, but not a lockdown. And I think that's the kind of thing that we need to have: a really thoughtful discussion, an understanding of what did we accomplish? What didn't we? Again, not to point fingers or to lay blame, but to say, "Do we want to do that again?" Or, "What should we do again?" I kept hearing people talk all the time about how long it would take to get those first doses of vaccine out, and I think that's a very important mark, but even more important is how long will it take to get the last dose of vaccine out? Meaning, who in the world doesn't have access to it at that point? And we didn't really do that at all. We saw many areas of the world that never had access to vaccines in the first few years of the pandemic. I think these are all the kind of lessons we want to really take to heart. And that's where our trust will come from if we have a very transparent and we have a very open and honest discussion, a review of what did we do? What could we have done differently, what could have been done better? What really worked? And I think that would really help us both with the trust issue and it would make us better prepared for the future.

Chris - Do you think we are better prepared for the future? If Covid mark two came tomorrow, do you think that we would rinse and repeat and make all the same mistakes again, or have we learned the hard way and we are now going to handle it so we are much better prepared and it will be over in a flash next time?

Michael - I think your concept of rinse and repeat is a very important one. I actually really like that visual. The challenge we have is that it's not just what we do, but what will the public do with us? And I believe we're in worse shape right now than we were in 2020 because we have lost the trust of much of the public around making recommendations from a public health perspective. And again, public health is one of those activities where it is critical to have the participation and the support of the public in whatever you're going to do in terms of trying to avoid infections, reducing serious illness, hospitalisations, and deaths. And so to me, I am more concerned right now that in this era of anti-science, where the most important thing some groups can do is just demonise the personnel in the public health or medical community trying to save lives. It seems if that were something we talked about 5 to 10 years ago, nobody would have believed it. You know who the bad guys are. And so that's something we have to overcome for the next pandemic.

A map of the world showing hotspots of an infection.

How do we communicate with the public in the next pandemic?
Linda Bauld, University of Edinburgh

Regular listeners will know that Chris Smith was pretty busy at the start of 2020, when an unknown flu-like virus first emerged in the Chinese city of Wuhan. At that time, and over the course of the next few years, he was invited to appear on national and international networks with Linda Bauld, professor of public health at Edinburgh University. Chris has been catching up with Linda, and began by asking her at what stage the public should be told about the outbreak of a new pandemic...

Linda - I think that's a difficult decision, Chris, for any government or public health agency. I've been co-chairing the behavioural and community engagement group for the Scottish Standing Committee on pandemics. So here in Scotland we have our own pandemic preparedness that we're now engaging in looking ahead to future threats. I think it really depends. We don't know what the next pathogen will be, but the key principle for me is transparency. So once there is an outbreak, it could be localised. It could be something that people are concerned about and is picked up through health protection. It needs to start with engaging with the relevant authorities, others in the health service and the public health system. And then if we know that information needs to be communicated to the public because there is a potential risk, then I think it's important to do that early. Not to panic people, but to start that communication as quickly as possible. And I think that's one of the lessons that we've taken out of COVID that maybe that didn't happen at the pace it should have done.

Chris - On the flip side of that though, people have criticised us, not you and me, but the scientific, medical, and also political establishment because we said things that we thought were true, then we changed our minds. Now obviously it's reasonable to update your understanding and update your stance based on a changing situation and the acquisition of more knowledge. But people, it feels, want concrete information, not unreasonably. But that's not possible to supply all the time when you've got a dynamic and emerging situation going on.

Linda - No, I think transparency also needs to include uncertainty. So let's just use a couple of examples here. I mean, there can be e-coli outbreaks, or we saw concern about RSV, a respiratory virus recently. Or we had mpox in the UK that we know affected particular communities. It's about saying there's something that's arisen, there's action that the public can take or we just want to let you know about this, but actually we're unsure what the science is telling us. We're waiting for more surveillance, waiting for more testing until we can give you more accurate information. And in the meantime, these are the practical steps you can take. For example, engage in good hygiene practices. If it's something to do with food, tell people where you've been. Look for particular symptoms amongst the people that you live with or your community. Basic information and then say, we'll update you once we know more. And I think communicating that uncertainty is really difficult for decision makers and probably at those early stages it needs to be public health authorities that do that before we pass on to others.

Chris - Michael was saying, quite alarmingly, that he feels that trust has been dented quite significantly damaged because of COVID. Do you share that view?

Linda - I'm a bit more optimistic than Michael. I think there has been a lot of misinformation that has circulated. Anti-vaccine sentiment, questioning about the measures that were taken. And let's face it, there's inquiries now that will pour over all of that. But I think the public is better educated now, particularly about infectious disease and are asking more questions. I think if you look globally though, it's not always the case to say. It might be the case in the US and the Uk, but I wouldn't say in some of the countries that my colleagues work in, that COVID causes major distrust between the government and the public. I think that bond is still strong in many places and we probably need to learn internationally about how to manage that better.

Chris - So who do you think are the right sources? When there is a pandemic situation, who should be giving out that information? Because we are in our module two of the UK Covid inquiry and there's been some quite interesting speculation and comment around some of the opening hands that have been played in the inquiry. Including some of the things that Sir Patrick Vallance wrote in his diary, who was our Chief Scientific officer at the time of COVID, wasn't he? Saying that there was a sense that perhaps the scientists were being pushed out there in front of the government so the science could be blamed rather than the policy makers so much? Who is a good source for this sort of information? Should it come from the government? Should it come from scientists? Did we get that right during the pandemic?

Linda - Well, I think there's a lot there. The first thing I would say for any government, and I work with the Scottish government, is that this is a long running programme that needs to be in place in advance of any future health threats. The connection between authorities and the public, the connections and relationships amongst the public, inequalities between groups, capacity to communicate. We need to make sure we've got that in place and we maintain it in between health threats. In relation to who should communicate, the problem with politicians doing the communicating about health issues is they are not the experts. So I think it's important that we differentiate. So we have a communication function, for example, through public health agencies etc, where we say, this is what we're communicating about the science. But when it comes to this is what is happening to you, the public, and these are the bits of laws or decisions that are going to impose on your lives, and this is what we want you to do, that needs to come from the politicians because they're the decision makers. One thing I would say about pandemic communication, if I could have redesigned it, I would've separated out the scientific advisors and the public health experts in terms of their communication from the politicians. I don't think they should be communicating together because then it looks like science is essentially condoning all the decisions the politicians are making. And we know that politicians were faced with very difficult decisions, and it wasn't always about the scientific advice.

Chris - So the approach that was taken by Number 10, Downing Street, where they had that podium, prime minister in the middle usually. Or one of the senior cabinet ministers flanked by usually one of the senior medical officers, chief medical officer for example, and then one of the scientists to the other side would, would you say that was a bad mix? They shouldn't do that again.

Linda - I think if we could think about it differently, we might have press conferences with answering journalist questions where you have that combination. Not necessarily broadcast on television, but I think it would've been better actually if you could have taken the politicians out of the mix and have the briefing, just a basic scientific briefing. This is what happened today. This is what we think is going to happen tomorrow with just the scientific advisors, without the political decision making being rolled into it. And I think if you look at some of the approaches in other countries, it was primarily the public health agencies who communicated in a particular way and then the governments were also passing on other information. So I think we need to think about that really carefully during future public health threats. And then the final point for me on this is locally we mustn't forget the local context. So you have in the UK your director of public health or maybe community groups who are broadcasting through local radio. They need to get the information from the government and the public health agencies and share that with their listeners and their audience in a locally appropriate way. So it's a tiered approach.

An artist's interpretation of a coronavirus particle.

How do we prepare for the next pandemic?
Maria Van Kerkhove

Should the next pandemic come to pass sooner rather than later then governments and the World Health Organization, the UN agency responsible for keeping us well, will once more be thrust into the spotlight. Chris Smith been speaking to Maria Van Kerkhove, who leads the World Health Organisation’s work on emerging diseases, beginning by asking her whether another pandemic was inevitable...

Maria - It isn't a matter of if, it's a matter of when, which is why pandemic preparedness is so important for governments and organisations like mine, like the World Health Organization. It is important that we are ready. We are agile, we can act rapidly so that we could prevent these from happening if possible. But if we do see events like outbreaks and epidemics, we have the possibility to mitigate them, to limit their impact on a global scale.

Chris - Now, people like yourself have been saying that for a very long time, but we still got caught out by COVID. Why?

Maria - Well, there's a number of reasons why we were caught out. I mean, I think the world was preparing for an influenza pandemic, and influenza is something that we expect to circulate and to change and to have pandemics from. But we've never had a pandemic from a coronavirus before. And people like me here at the World Health Organization and in institutions around the world are preparing for things like this. But governments are dealing with so many different challenges for their populations. Infectious diseases are one of them, but infectious diseases emerge in the context of many other challenges. Like war, earthquakes, fires, economic crises. So it's not something that everybody is at the ready for at any moment of any day.

Chris - But surely the learning points in the last three years argue we're not doing enough, and we should be.

Maria - Absolutely. I mean, I'm not saying that that's right, that we're not ready for this. And I think we have globally learned so much from the COVID 19 pandemic. We've learned the ability to act fast and to rapidly mobilise what you have in your country. Whether it's about surveillance, to be able to identify cases. To make sure that they're cared for properly, to have clinical care, to have testing available to ensure that patients who need to be treated have access to therapeutics. To make sure that we have systems in place to not only develop safe and effective vaccines, but to actually use them. So we do need governments at the ready. And I think the trauma that we've all lived through in the last three and a half years, it's still fresh in our minds. It's something we have to use to propel us to keep up the momentum. The world's capacities to deal with pandemics have greatly improved in the last three and a half years. The challenge right now is the political will and the financing to keep up that momentum and to sustain the gains that have been made during COVID 19.

Chris - What changes has the World Health Organization made off the back of COVID?

Maria - We are a member state organisation, which means we work for governments around the world. We work for everyone everywhere. And what we try to do is to support governments in building capacities and sustaining capacities. We are working with all countries around the world to see how their response to COVID, where they were operating in a crisis mode, how the work can be calibrated to meet the needs of COVID right now because COVID isn't gone. But also the next threat is that, some of which we know some of these pathogens that are circulating, but there may be a new pathogen that's out there. We've worked to increase capacities from a scientific level. For example, say the development of safe and effective vaccines to make sure we have better production capacities around the world, not just in high income countries or in one particular part of the globe, but to make sure that there are more companies that can actually produce these safe and effective vaccines. And we're working not just on the scientific side, but also on the political side, to have statements from political leaders to ensure that we are much better prepared for the next one. And so these high level political statements, which may not sound important to everyone, are really historic because these are commitments shown by world leaders that we have to do better the next time. It's not just about a handshake saying we could do better. We have to do better the next time because these devastating impacts that COVID 19 demonstrated showed that we have to be much more collaborative. We have to be cohesive and equitable in our approach to not only responding to pandemics, but also to preventing and preparing for them.

Chris - Are all governments coming to the table and cooperating, or have we got any weak links in the chain? Are there any areas where we need to bolster our response and our presence as an international community, a medical community? Because obviously those are the places, if they're a weak link, where they're ripe for something like this to either take, hold or start in the first place.

Maria - That's a very complicated and important question with many different components. Countries are coming to the table to have this discussion. We've all gone through this collectively, and there is a willingness to ensure that we leave the legacy of COVID better than we started. There are a lot of weak links, not necessarily by countries, but by topic. You know, if we look at surveillance, do we have good surveillance around the world to detect the known pathogens that are circulating or could be circulating? And the next one, the next 'disease X', as we call it, which represents an unknown pathogen, and COVID 19 was disease X. So the next X we say is out there. We've worked really hard to ensure we have better supply chain management, better scientific achievements in terms of collaborations and addressing some of the unknowns about these pathogens, how they circulate, where they circulate, who they impact. A very big gap we have right now is around equity and access. And that is something that we need to continue to work on. So it's not only important that we have medical countermeasures, that we have diagnostics, therapeutics, vaccines, we have personal protective equipment. We need to make sure that the use of these life-saving interventions are available to those who need them most. We need equitable access to these materials around the world, and we have a long way to go to achieve that.

Chris - One thing that you haven't put on your list, there is the issue of information sharing and transparency. And the last time you and I spoke to each other, you were making international headlines because you'd penned a fairly forceful piece in a major scientific publication calling out what you saw as bad practice on the part of information sharing from China, who had not revealed quite a lot of information about what they clearly knew about the early days of the pandemic. What's happened in the aftermath, if anything, of you saying that?

Maria - Information sharing is a critical one. We think about surveillance or we think about data gathering on patients and clinical management. All of that information that exists in a country, in a hospital, in a market, you can pick the location. It's only as good as it is shared, meaning that if it's kept amongst those individuals that collect that information, it is not shared for discussion with other disciplines, with other institutions, with other countries, we can't learn from it. We work on the foundation of strong science collaboration, because none of us work alone. No matter what institution you work for or what discipline you come from, you work with others, you collaborate with others. But we need to have trust amongst individuals, between countries, between institutions, between individuals. And we need transparency. I think on a global scale, there are a lot of efforts to increase robust data collection. So better data collection, not just more, but to be able to share that in a way that leads to action. So yeah, I did pen a pretty strong piece, but I've been speaking like that for quite some time. We, as the World Health Organization, can only act on the information that we have. And for the most part, we have a lot of collaboration, a lot of information that is shared. If we think about the next pandemic, we need strong surveillance in animal populations at the animal human interface in people. Because many of these diseases that we're talking about are zoonotic, what we call zoonotic, meaning they transmit between people and animals. And if we don't have strong surveillance, then we don't have the ability to detect something fast. But if we don't have that information shared, we won't have any visibility on what is actually happening, which means we will not be able to limit the impact of these spillover events. And what I mean, spillover, I mean the transmission of these pathogens from animals to humans. This happens all the time and it doesn't cause an outbreak or an epidemic, but sometimes it does. And when it does, we have to be ready.


Add a comment