From William H. McNeill, Plagues and Peoples (1998), pp. 182, 185:
“[In the Mediterranean port cities] until the seventeenth century occasional plague outbreaks, carrying off anything up to a third or a half of a city’s population in a single year, were normal. Venetian statistics, for instance, . . . show that in 1575-77 and again in 1630-31, a third or more of the city’s population died of plague.
“Outside the Mediterranean, European exposure to plague was less frequent . . . and, at least sometimes, also more catastrophic. . . . In northern Spain, 1596-1602 . . . half a million died . . . . Subsequent outbreaks in 1648-52 and 1677-85 more than doubled the number of Spaniards who died of plague in the seventeenth century. Pasturella pestis must thus be considered as one of the significant factors in Spain’s decline as an economic and political power. . . .
“. . . The plague did not disappear among populations living closer to the Eurasian steppe reservoir, nor did it diminish in virulence . . . in those regions where it continued to manifest itself. . . . Changes in housing, shipping, sanitary practices, and similar factors . . . were the decisive regulators, both in the advance and in the retreat of plague.”