Instant Genius - Why we are seeing the return of infectious diseases

Episode Date: March 1, 2024

In the first quarter of 2024, infectious diseases including measles, plague, and cholera have all reared their ugly heads again. Are we seeing an unprecedented level of disease re-emergence? Why do they come back? And what would it take for another Black Death to happen? To find out, we spoke to Paul Hunter, Professor in Medicine at UEA’s Norwich Medical School. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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delivering digital precision with analogue warmth, so you can experience exceptional sound at home. Music just as the artist intended. Visit name audio. to learn more. This is Instant Genius, a bite-sized masterclass in podcast form. I'm Noah Leach, news editor at BBC Science Focus. Already, the first two months of 2024 have seen outbreaks of measles in the US and the UK,

a global shortage of the cholera vaccine, and even a case of bubonic plague for the unlucky owner of an infected cat in Oregon. Infectious diseases we thought were long gone are resurfacing, and it may be seem as if your vision of the world has been blurred by a kaleidoscope of diseases. But how much disease re-emergence is normal? To find out, we spoke to Paul Hunter, professor in medicine at UA's Norwich Medical School. Paul tells us about why these diseases make a comeback, the terrifying truth about where the last strongholds of diseases are kept, and what it would take to plunge society into another black death. So, Paul, there are diseases that just stick

around in society that we've become familiar with, but they've all come from somewhere. And I understand this is split into infectious diseases that emerge and diseases that re-emerge. So how often does diseases that we think are gone just come back? The issue is whether they've actually gone or not. And a lot of infections maybe were common wants and still spread within society, but then come back with the force at some point in the future. I think if you're looking as emerging infectious diseases, as a whole, that's new diseases and diseases that came back. We typically around the globe will see one or two significant emergencies, or re-emergences, a year about on average. And if you look back over the years, the new infections that were around since I qualified,

particularly HIV-AIDS, COVID, of course, a range of other influenza-type viruses that have have re-emerged and disappeared. And yeah, there's many of them. But really classic infectious diseases that re-emerge, it's difficult. I mean, it, on a global level, they've probably all been there pretty much all the time. But it's more on a regional level that when like cholera spreads into an area that it's maybe not caused problems for decades, as we're seeing at the moment. So is it ever possible to well and truly eradicate an infectious disease, wipe it from the face of the planet? We did it with smallpox. We thought we might be able to do that with poliomyelitis, but at the moment it's not looking good. So generally not. I think most infections, I don't think we really expect to ever eradicate them again.

And sometimes you get a new infection like we saw with SARS in about 2003. a similar virus to COVID. And that we manage to eradicate. But once the infection spreads globally and through society, they're almost impossible to eradicate. You can manage them. You can control them, but very rarely eradicate them. So what makes smallpox different? Why are we so happy to say that that one's gone? And is it gone for sure? Yeah. Well, it is. There are still some laboratories around the world, a very small number that still have smallpox virus. And there is a concern with smallpox that at some point it could be used as an agent of warfare or a bioterrorist agent, but probably outside of the US and Russia, there are very, very few labs that will have viable smallpox

anymore. It's important to be kept around because if there is an attack, then you need sources of the virus to gear up to do your testing and so on. on, but yeah, hopefully that wouldn't ever happen. And for the other viruses, why can't we get them to this stage? What makes smallpox so exceptional? Well, I think with smallpox, it was that it was a virus that the vaccine was very highly effective. And we had, at the time, a lot of will to get rid of smallpox.

It was a very dreadful disease. It left people, even if they survived, most people did survive, but they often had quite severe facial scarring and that had severe implications for the rest of their lives when they'd got severe smallpox scarring. But we had vaccination that worked. It was a disease that we could diagnose fairly easily and therefore you could tell where it had spread to an area. People were on the lookout for it. You could spot it. And we developed a strategy called ring vaccination where if you had a case in a village in Africa, you would go and vaccinate the whole village. And by and large, that worked very well.

There are a number of problems now. The first is that not all infections, indeed, many infections are infectious before somebody gets sick, as we saw with COVID. So trying to control something that people who are otherwise well can spread is, well, not impossible, or trying to eradicate it anyway. The other is that these days,

I think the will to do that sort of activity is more difficult, and particularly in some parts of the world where there's conflict, trying to achieve that is really difficult. We saw in Democratic Republic of Congo, DRC, there's been a quite a severe Ebola outbreak, and we can control Ebola outbreaks. We've got vaccines now, but we weren't able to control that as well as we would have done, in part because people going into areas where cases were occurring were being shot at and murdered because there was conflict in the area and things like that. So, you know, when you've got those sorts of things happening in the world, trying to implement public health campaigns to eradicate a disease isn't going to work that well.

Could you tell us what some of the other key reasons are that infectious diseases can come back? Yeah, well, the first is that the virus might evolve. We see this particularly, with influenza, where the virus evolves over time. And sometimes you can get a big step in evolution, which makes that virus then spread quite more rapidly in its own for a while. And those are what's called, usually what's called escape mutations. And we saw this with COVID, where we got mutations coming along that didn't actually negate prior immunity, whether that came from vaccine or a previous infection, but certainly reduced the effectiveness of your already acquired immunity to prevent the infection. And we see with COVID that typically, you know, people,

well, in England now probably, on average, every single one of us has had three infections of COVID so far since the start of the epidemic. And that's very difficult to eradicate. The other is how the disease spreads into humans. There are some diseases like plague that is there all the time. It's in the environment. There's something called Sylvan. attic plague, which is where the plague spreads in rodents. And in America, it's typically prairie dogs that you sound to think about. And something might happen to the environment that suddenly brings people into contact with those animals. So in the US, you see the occasional case of plague in people who are hunters or, you know, they get too close to prairie dogs,

thinking they look cute, that sort of thing. And they can pick it up. Then in Madagascar, a couple of decades ago, they had a big outbreak of plague. And the view was that up until that point, plague was actually quite uncommon in Madagascar. It was still there, but it wasn't that common. And in part, that was because the rats were the brown rat. And the brown rat doesn't come into contact much with humans. Generally, it lives in sewers away from humans. It's the black rat, that ratus ratus, that's the main risk. And that risk is primarily because it lives close to humans around the world. It used to live very close to humans in medieval times in Europe, and it still does in many parts of the world. And I think what was happening there was primarily that there was a lot of

environmental degradation. And then the rats that were living in contact with humans were then coming in contact with other animals that were infected with the plague, infecting the rats, and then the rats were then spreading the disease into humans. So environmental degradation, is another big risk factor. The climate is changing and that is affecting the distribution of many diseases. There are diseases spreading into areas where they've never been seen before or they've been rarely seen before. We're seeing in Europe along the Mediterranean coast, we're starting to see small outbreaks of dengue fever, which we've never really seen before. Another reason is reduced vaccination availability or reduced vaccination uptake. And I think that's what's driving the

problems that we're seeing with measles in the UK at the moment is people, you know, they've never seen cases of measles. You know, I had measles when I was a child. Most people in my generation did, but if you're a lot younger, you've never seen a case of measles. Why do you want the vaccine? And why is that once your vaccine note takes drops in a society, then measles can start to spread and this is what we've seen here. I think those are a few of many different possible explanations of why diseases might reoccur. It's peak pollination season, and my business is scaling fast.

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So how different is this disease nowadays to back then when it caused such widespread destruction and death? Well, I think as far as I can tell, there's not actually that much difference in the organism. It's a bacterial infection, and the name is ear-scentral, Sinia pestis is the name of the bacteria. You're quite right. It typically spreads from rats to humans via flea bites. It can be just as bad as it ever was, but because it's a bacteria, we do have antibiotics to it and we are able to treat it in a way that we just didn't have or they didn't

have in medieval times. So yeah, it can still be very nasty, it can still be fatal, but it's a lot easier to treat. And so people shouldn't be dying of plague. anymore, even if they catch it with adequate treatment. So obviously this case was kind of isolated and treated before it could spread into the community and beyond and presumably because of what you say that it's easily treated. But how easy would it be for it to get out of hand? I mean, what would it take for another black death to kind of effectively begin? I think you're looking at sort of a collapse of society and that to a certain extent was what was happening in Madagascar when they had their plague epidemic. There was also another epidemic of plague in the Democratic Republic of the Congo

as well, a bit more recent than that. And again, a lot of that is conflict, environmental collapse, economic collapse, all coming together so that people are living more closely in contact with animals that could be transmitting the infections. Rats that live closer to humans, the black rat, may be foraging more widely and picking up plague from animals in the forest, surrounding forests, where if an animal in the forest has got plague, but it doesn't, you know, no humans come into contact with it, no human's going to get the plague. But if those rats then start coming into contact or people start foraging in the forest for food, game, wild food, then they can come into contact and then it can spread.

And you do get some spread person to person with plague as well. And certain burial practices can exacerbate that. After COVID-19, do you think that we are prepared enough for the next pandemic, whatever and whenever that may be? That's a difficult question. I think I sort of have quite a cynical view of political will, really. And I think people will probably be very engaged and prepared for a few years. years, but whether you can maintain that preparedness for 10, 20, 30 years before something as big as COVID comes along, I doubt. I suspect, you know, once the next generation moves into positions of power, then what we've learnt now will not be as well thought of and as well remembered as it should be. I think there are some things that change. I think science has advanced quite a lot with COVID, particularly around the rapid development of effective safe vaccines. But in terms of the rest of it, the political will to make changes that are needed early enough to have a big impact, I think, in 30 years' time, if we're still here. I think a lot of those lessons will have been forgotten, to be honest. One of the lessons that we've learned was around tuberculosis. You know, the US

ran down a lot of its tuberculosis control programs a few decades back and then suddenly found that actually tuberculosis started spreading again in the US and possibly cost a lot more to resolve than ever they saved from reducing the spending on the prevention programs. And I think we need to maintain the ability to respond. So obviously, COVID emerged. And for the moment, it doesn't feel like it's re-emerging it in a way. It still feels like it's right at the beginning of that kind of emergence. But if you had to choose which the worst disease would be to come back from the past, what would it be? I mean, surely the black death is up there. but if we can treat it easily.

Yeah, I mean, I couldn't imagine Black Death causing the same sorts of problems in Europe, certainly in Western Europe that we've had. I think cholera is a major concern in some parts of the world. And it's the thing that I would worry about most, particularly in Ukraine and in Gaza, both conflict areas that currently don't have any cholera, as far as we were aware. but if it did get there, it would probably spread very rapidly in their populations and cause untold numbers of deaths. And so these are threats. I think the thing that probably would cause most fatalities, if it came, would be another big influenza pandemic like we had with the

Spanish flu in 1917, 1918, which actually came from a pig farm in America, not from Spain, even though it's called Spanish flu. It was probably, the first human was probably working on a pig farm in Midwest United States. And if we got another flu virus like that, then we would see many, many millions of deaths again. And the Spanish flu as well, it tended to kill younger people. COVID tended to kill older people. And it was a very unpleasant death, the Spanish flu, if you were going to die from it. very unpleasant. It was, you know, your sort of lungs filled up with water and you sort of effectively drowned in your own respiratory secretions. And it was a dreadful. And I think that has the potential to kill more people than most of the other infections. Although, you know, as we've seen with COVID, there's been still many millions of people have succumbed to COVID. So, Paul, you've mentioned war a few times. And so let's come onto that. You've said that it can lead to the destruction of health services and infrastructure like water treatment.

facilities. It also leads to mass migration and or people living closely with each other and with animals. So all of this significantly increases the incidences of infectious diseases, both emerging and re-emerging. That's the sounds of it. So with the current global conflicts in Ukraine, Gaza, beyond, do you expect us to see a rapid rise in infectious diseases this year and in the future? I think with Gaza, we're definitely seeing substantial numbers of infections. It's very difficult to know for certain what the exact position is in Gaza at the moment, and the information generally comes from one side of the conflict or another, so how valid a lot of the data are, but I think one thing is clear. We're seeing a lot of diarrheal disease in Gaza, and a substantial

proportion of child deaths, deaths in children under five are probably due to diarrheal disease. And some of the reports from WHO suggests they're seeing about 20 times the incidence of childhood diarrhea compared to previously. And so, yeah, that would be a big risk. The concern often is when you've got conflict situations, you've got diseases that spread. And depending on where you are in the world, there are other diseases that can spread during conflict settings. We've already talked about Ebola in the Democratic Republic of Congo. And these are infections that can travel. You know, people can leave the war zones, move elsewhere, or indeed move into the war zones. And we saw in Haiti, There was the big outbreak of cholera in Haiti about 20 something years ago after the earthquake.

That was brought into the country by troops that had been sent there to help recovery from the earthquake and contaminated water sources that then infected lots of people and the disease spread and caused an even bigger tragedy. And you've also said that there is a shortage of the cholera vaccine globally. Why is this? Is this because of war? Well, there are a number of reasons. I think partly because a lot of vaccine production efforts moved to COVID and were impaired by the COVID pandemic with people not being able to work and so on, partly because of the demand, because cholera infections have been going up in the last two or three years globally. So there's more demand for the vaccine. And we typically globally store a lot of cholera vaccine. We have a global cholera vaccine store. and I was told only the other week that that store now has a negative value because everything in the store's gone and everything that they're making in the next few weeks has already been allocated out to countries where cholera's a problem. So that I think is a contributory factor to the problems that we're seeing with cholera in the world.

And obviously COVID-19 and from what you've told us, actually Spanish flu as well, spread so rapidly and so effectively through global travel. And this seems to be the case for a lot of diseases that reemerge into societies where they've been absent. I mean, if you ever travel abroad, particularly out of Europe, you may be advised to get some vaccines when you go to certain countries. So how can we lower the risks of bringing back a kind of unwanted souvenir when we go abroad? Well, I think the first thing is that one of the biggest threats of overseas travel is antibiotic resistance organisms, which some, including myself, would characterize as emerging infections. These are infections that have been around for some time before, but now we can't treat them

because they're resistant to possible drugs. I think one of the biggest concerns with bringing infections from overseas is sex tourism. And we've seen this in the past with drug-resistant gonorrhea. particularly people going out on sex tourism to places like Thailand, for example. I think that was in part an explanation for the monkeypox outbreak, the M-Pox outbreak that we saw a year or so ago. The other issue as well for antibiotic resistance organisms is medical tourism. People from the UK or Western Europe might go to India or Turkey or other places because if you want a cheaper plastic surgery or even dental reconstruction surgery of that, you can get it done

cheaper and probably quicker by going to some of these other countries. The concern is, though, the potential for bringing back antibiotic-resistant organisms that you would not necessarily have been exposed to in this country. And that there's a lot of evidence that that has also contributed to the spread of some of the more highly resistant organisms that we see circulating today. Another huge concern on everyone's mind is, of course, climate change, which you've mentioned already. And obviously this will impact the emergence or reemergence of diseases. We've actually done a podcast episode before on the zombie viruses being released from melting permafrost. So what else could be kind of lurking in the pockets of our past world effectively that we don't want to

expose and cause to reemerge? Yeah. Well, actually, I wrote an article on zombie viruses. Those viruses are very unlikely to actually cause disease in humans, the zombie viruses that were thousands of years old. But that doesn't mean to say that there is nothing of concern there. The thing about the permafrost is that it does enable certain viruses, certain bacteria, particularly to survive. In Russia, in the past, there have been outbreaks of anthrax, where people believe that what was happening is that reindeer carcasses from previous out. that were being lying in the permafrost suddenly became available again and that anthrax can remain viable for centuries in the right conditions and then maybe I don't know some carnivores or other got infected and we got another outbreak and there were human fatalities in some of those outbreaks.

The other concern is burials in the permafrost actually. A lot of deaths in northern Europe that who were buried in permafrost, around 100 years ago, died from influenza. So there has been concerns that the virus could still be there. And in fact, people have actually dug up corpses in areas where people died from flu and have been able to demonstrate at least parts of the virus, but probably not enough for that virus to remain infectious. And even if there was, probably it wouldn't cause as much harm as it did 120 years ago. The big concern, I think, is smallpox. Smallpox isn't thought to live for many decades,

but in right conditions, probably a few decades. And so there is the potential if somebody came into contact with a human corpse that had died from smallpox and then been buried in permafrost that could then infect them. I mean, that's the theoretical risk. I think it's unlikely, but I don't think any of us would want to exclude all possibilities of that. The return of the only one that we think has gone. Let's hope not. Yeah, absolutely. That would be an absolute nightmare if smallpox came back. And as someone researching in this field, could you share something that you are particularly excited for us to learn or discover about infectious diseases or something that you're currently working on? My project that we've just started is looking at extreme weather events in low-income countries and how to make health services more.

resilient. I think a lot of the research on climate change to date has been on what particular diseases that might move into areas. And we've done this. We've been looking at dengue fever and risk in Southern Europe and in Latin America. But I think there hasn't been a huge amount of work looking at the impact of climate change through disrupting society and the impacts that could have on human health in the future. And that's the area where my group will be working on for the next four years. That was Professor Paul Hunter on infectious diseases and why they reemerge. Thank you for listening to this episode of Instant Genius, brought to you by the team behind BBC Science Focus magazine.

By the latest issue of science focus in your favourite shop or visit us online at sciencefocus.com. This podcast is sponsored by name, audio and focal. The texture and emotional depth of music can be lost through digital sources or poor signal. Name Audio believes you can have digital precision with analog warmth. Alongside French acoustic specialist focal, Name creates high-end audio systems combining innovation with craftsmanship, so you can listen to music, just as the artist intended. Discover more at name audio.com.

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