ABSTRACT
In this chapter, the author advances the idea that diseases are interrelated and therefore that "plagues" cannot be understood in isolation. The author discusses the effects of a plague need to be judged not only by the characteristic mortality of the outbreak and the long-term trends of the disease in question but also by changes in all diseases in the wake of the plague. The 1918-1919 influenza pandemic, sometimes called the "Spanish flu," was most deadly outbreak of any disease in the twentieth century. The entire influenza mortality curve in 1918 lies above the 100 per 100,000 line, reflecting the severity of the epidemic. Despite the magnitude of the 1918-1919 flu and its peculiar age-mortality profile, demographers have paid relatively little attention to it. Historical epidemiology is an endeavor that strives to be good historiography as well as good epidemiology.
