The remarkable Books of the Dead from early modern Milan and the parish and tax records of Nonantola during the plague of 1630 allow historians to reconstitute the patterns of family and household deaths caused by pestilence. Not only did deaths caused by this highly contagious disease cluster tightly within households; the intervals between household deaths were also extremely short. As much as one-quarter of all plague deaths were multiple household deaths that occurred on the same day. Similar to a deadly influenza, the speed and efficiency with which the late medieval and early modern plagues spread depended on unusually short periods of incubation and infectivity.