And the reason why we think that it was due to trade is that there's some evidence in Han China during this first plague of similar symptoms, of a similar plague. But it really affected Rome. In these plagues, it's estimated that as much as 10% of the population might have died. In certain cities, it might have been 25, 30% of the population. Some historians even point to these plagues as destabilizing the Roman Empire. And this is a theme that you'll see often in world history, where if you have a population that doesn't have exposure to something, say smallpox, and all of a sudden they encounter a population that does have exposure, well, that smallpox might wreak havoc. But it wasn't just disease.