Predicting the next pandemic

Why do new diseases, like Zika or Ebola, abruptly appear? And why do old diseases that have been around for decades at a previously low level suddenly become a problem? Chris Smith was joined by Colin Russell, who studies the dynamics of emerging infections at Cambridge University, and he explained first where new diseases come from...

Colin - There’s a huge diversity of pathogens that infect animals all around the world and when those pathogens start infecting humans and evolve the capacity to transmit efficiently from human to human, we have these big dramatic outbreaks.

Chris - Taking Zika as an example of this - we’ve known about Zika for a long time - so what’s changed to make Zika suddenly start spreading and infecting people the way it has?

Colin - Goodness gracious! If I knew the answer to that I’d be at home writing a paper right now.  The short answer is we don’t know and it’s one of the critical questions that people are looking into right now, which is - we’ve seen this virus and we’ve known it infected humans for a long time but historically it’s been a mild infection and now, suddenly, it seems to be causing severe disease but we don’t understand what’s changed.

Chris - So something has to change either in the bug itself or something changes in the environment the bug inhabits or something changes more broadly on the scale of the whole planet and us, which adjusts or tips the balance?

Colin - If we look at smallpox, for example.  Smallpox circulated in Europe for hundreds and hundreds of years but before European explorers went to the Americas, smallpox wasn’t in the Americas.  When European explorers went to the Americas they introduced smallpox and smallpox decimated, literally decimated, the North American populations and so there is that possibility for that access to a new population that can facilitate the sudden, dramatic, outbreak.

Chris - Some people have speculated that what we’re seeing in Brazil could have been the result of an introduction to the country in sporting teams, either for the World Cup or people in rowing competitions from pacific islands where Zika was circulating.

Colin - So, one of things that researchers are looking into right now is how and when did the virus first make it to the Americas?  It was known to be circulating in parts of French Polynesia and other pacific islands and, at some point, the virus was introduced into the Americas.  We don’t know when, we don’t know how many times?  But by virtue of the fact that we’re an increasingly globally connected world where people are travelling all over the world all the time, the possibility for introducing new diseases is always present.  There are so many different viruses that are circulating in animal populations all over the world that the more we look at those viruses, the more viruses we ultimately see and we get a very difficult challenge there of then anticipating which one of them is most likely to start causing problems for humans because the vast majority of them, at least right now, don’t.

Chris - Therefore, what should we be doing to protect ourselves?

Colin - This is actually a really complicated issue because the places where emerging infectious diseases are most likely to first enter the human population, these are the places are the least capable of actually dealing with these emergence events.  So, if we think about the U.K., for example, we see very few actual emerging infections and that’s largely a product of the fact that we have very limited interaction with animals.  I’ve seen no wild animals today; I don’t have any chickens living in my home; I haven’t seen a pig in months but the simple fact is, in many portions of the world, that’s very different.  It’s a situation like that, where you have really close interactions between humans and animals that these viruses are mostly likely to emerge.

Chris - So basically, we’ve got a wonderful laboratory network in western countries like America, like the U.K., Australia, and they’re doing a great job of protecting countries where the risk is already low and what we need is to have that sort of network in countries where the risk is high?

Colin - So there’s two things. The first is we need to identify the places that are actually risky…

Chris - Do we not know them then?

Colin - No-one has done that precise risk estimate across a wide variety of diseases.  But, once we do identify those high risk areas, we have to develop the basic public health infrastructure that allows people to differentiate ordinary from extra-ordinary.  Because, in many portions of West Africa, for example, if you show up at a doctor's office and you have anything that might be considered malaria, you’re told you have malaria - go home but, the simple fact is, that there are probably people who are told that they have malaria and they, in fact, have something that’s absolutely not malaria.

Chris - I think the first man ever to have ebola was a school teacher who came home with a bad fever and was told - you have malaria and he then infected the entire medical team, his family and the village, and hundreds of people were spawned by the case so you are absolutely right.  Are you saying then that people need to be better at diagnosing these things and spotting these things sooner?

Colin - Well yes, absolutely but that’s not a trivial undertaking because to be able to make that kind of diagnosis that differentiates something that you see every day from something that’s actually kind of different, it requires diagnostic tools that just don’t exist in most portions of the world.

Chris - We don’t really skimp on spending on defence when it comes to warding off a marauding force from overseas.  Could we not regard this as a form of defence and perhaps we should spend a little bit of that money on those sorts of resources you’re advocating on the ground in these foreign countries because, at the end of the day, if something is spawned there it can sure as hell come anywhere to roost, couldn’t it?

Colin - Absolutely.  High income countries effectively have to see emerging infectious diseases as a real defence threat and this is becoming increasingly pervasive, particularly in the United States, where infectious diseases are being more widely regarded a threat to national security.   But it’s very much the case, because in these places where diseases are most likely to emerge, if we invest more in detecting those viruses or bacteria or whatever that ends up causing disease, if we invest more there, there’s a greater chance that we can stop it before it comes here.

Chris - And keeping an eye out for, basically, what’s out there?

Colin - We need some of that, yes…