 It was a pandemic of influenza that struck in the early months of 1918. It struck in, we generally say it struck in three waves. So there was a first kind of mild wave in the northern hemisphere spring of 1918, which receded in the summer or late spring. Kind of all the dates depend on where you were in the world. And then there was a second wave which erupted in the latter part of August and receded towards the end of that year. And then there was a third wave which was sort of intermediate in severity between the other two, which emerged in the early months of 1919. We think it infected about 500 million people, so one in three people in the world, alive at that time, and that it killed 50 million of them. That's the, those are the current estimates we work with. And the death toll could have been even higher because there was a big problem with under-reporting at the time. They didn't have a reliable diagnostic test. Undoubtedly, it was a concept. But to put in place a socialised medical healthcare system, a socialised healthcare system, is not an easy thing. You have to find a way to pay for it. You have to reorganise all your doctors in the way that you deliver healthcare. And so no country had really got around to it yet. And I think that the pandemic is what gave the stimulus to do that because there was a realisation that a pandemic was a global health crisis that you had to treat at the population level. You couldn't treat individuals and you couldn't blame. There was no point in blaming the individuals for catching an illness or treating them in isolation. So that was the stimulus. And you see from the 1920s countries, Russia was the first but then followed by Western European nations putting in place these socialised healthcare systems. And along with that comes epidemiology. The search for causes and effects and patterns in healthcare and in illness that is the kind of cornerstone of public health. If you can't see what's going on in a population in terms of health and ill health, then you don't know what measures to put in place. So the two go together. And so as a result of that, what happens is that the baseline health of population starts to become much more transparent, much more visible.