“For the influenza pandemic that erupted in 1918 was the first great collision between nature and modern science.” 

Barry makes grand pronouncements like this one throughout the book, and he sets up the reader to expect them in the Prologue. This pithy quotation also sets up one of Barry’s main themes: that the flu pandemic was the first medical outbreak to be fought with medical theories and accurate knowledge. Whereas the bubonic plague and other early outbreaks of the flu were fought by people who had rudimentary and often erroneous knowledge of medicine, by 1918, scientists around the world knew how to conduct research and how the immune system operated. Given the number of victims, it seems nature won the battle, while modern science won the war.

“The greatest challenge of science, its art, lies in asking an important question and framing it in a way that allows it to be broken into manageable pieces, into experiments that can be conducted that ultimately lead to answers. To do this requires a certain kind of genius, one that probes vertically and sees horizontally.” 

Barry pays special attention to William Welch, arguing that he is essentially the father of American medical research. However, he notes that Welch had one flaw: He was not a particularly good researcher. Instead, he was good at acquiring talented researchers and inspiring them. Those scientists could probe vertically—looking deeper into a topic to find new information—while also thinking horizontally—weaving together seemingly unrelated pieces of information. Science, according to Barry, is also about collaboration, so Welch’s role in creating teams is important, even if Welch himself never created new pathways of research or contributed direct scientific knowledge.