Disease is more common during a crisis: why?

Kyle Harper from the University of Oklahoma, is, unusually for our show, a historian, but we won’t hold it against him as he actually studies the history of infectious diseases. Author of 'Plagues Upon the Earth', Kyle is ready to pull on his historic expertise to describe what conditions bring about the perfect enviornment for disease transmission...  

Kyle - Right. And unfortunately conflict and humanitarian crises are very favourable for the transmission of infectious diseases. So pathogens that are viruses or bacteria, parasites that have to transmit between hosts, really benefit from situations in which human beings are crowded. And that's one of the main drivers of transmission in times of crisis. But there are other things too. If you think of the kinds of things that happen in crisis, we know that it leads to breakdowns in systems of hygiene and sanitation and so much of our daily lives and sort of unspoken routines and the infrastructure that we rely on for clean water, things that we're privileged often in the developed world to take for granted, but that have helped humans gain a kind of partial and fragile control over infectious diseases. Those systems tend to break down, particularly access to clean water becomes more difficult, sometimes in situations where it's already very limited or fragile, in conditions where you have refugees crowded into camps or people migrating in desperate circumstances. It also is partly due to the fact that these sorts of circumstances tend simply to undermine human biological well-being all around. So if people are hungry, it makes it much harder for their bodies to fight off infection, so they become more susceptible to infection and severe disease.

Eva - And are there any examples throughout history where people have actually managed to mitigate some of these risks and prevent big disease outbreaks in these conditions?

Kyle - I mean, I think in many ways, the one way to understand the last few centuries is interplay between infectious diseases that get in some ways bigger and more virulent and more dangerous and humans collectively responding, bringing together science-enlightened policy to tackle what really are collective challenges. And this one of the tricky things that of course we're living through with COVID-19 is realising how public health is public. Our health is very intricately tied together. And so it requires political solutions to address these kinds of challenges. But yes, I mean, I think one of the real triumphs of humanity is figuring out how to bring science, to work together, to do things like create giant sewage systems that handle the problem of human waste and that deliver clean water. So from quarantine and lockdowns, which go back to the late Middle Ages, through the rise of modern public health infrastructure and compulsory notification and vaccination, humans have done a good job at many times working together to address these kinds of challenges. But obviously we're not all the way there yet. And we still face very grave threats to our collective wellbeing.