During the last 1500 years, Rome was the inspiration of artists, the coronation stage of German emperors, the distant desire of pilgrims, and the seat of the Roman popes. Yet Rome also lies within the northern range of P. falciparum malaria, the deadliest strain of the disease, against which northern Europeans had no intrinsic or acquired defenses. As a result, Rome lured a countless number of unacclimated transalpine Europeans to their...