Harry S. Truman famously said, “There is nothing new in the world except the history you do not know.” Each day we are facing a crisis that some describe as “unprecedented.”* Serious? Absolutely. Life-changing? Unquestionably. Worthy of all our attention? Definitely. But unprecedented? Thankfully, historians are speaking up to help make sense of what we are facing today, and to provide hope for what can come. John M. Barry — who, in Rising Tide, wrote one of the best histories I’ve read of how a disaster changed our country for the better — has also written a book that is invaluable in understanding our current crisis. Barry’s 2004 work, The Great Influenza: The Story of the Deadliest Pandemic in History, makes him the historian who arguably knows more than anyone about the 1918 flu influenza that is the public health event most often compared to today’s outbreak. Barry writes that in that year, “a new respiratory virus invaded the human population and killed between 50 million and 100 million people — adjusted for population, that would equal …