ContributionMilitary attempts to spread bubonic plague illustrate belief in contagion.
NotesWhile besieging the city of Caffa, on the Black Sea, Tartars catapulted corpses of plague victims over the walls of the city. Western belief in person-to transmission-person (as distinct from miasmatic transmission) was also strengthened by the introduction of smallpox to Europe by returning crusaders and by the later introduction of syphilis to Europe by travelers to the New World. By 1800 there would be not only recognition that all three diseases were acquired from 'contagious effluvial' emanating from infected persons, but also recognition that the contagious material produced a specific disease (not different diseases in different individuals, depending on circumstances (climatic, constitutional, moral, etc.). Even by 1800, however, germs would not be a recognized factor (despite occasional speculations about their existence and possible role).
Pathogen ClassGeneral

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