Boccaccio, _Decameron_
Boccaccio's Decameron is a collection of tales collected ca. 1350, introduced by a frame narrative in which the plague of 1348 leads a group of aristocratic ladies and gentlemen to flee the city of Florence for the refuge of country villas, where they tell the stories of which the collection consists.
For a full text (including especially the "Induction," which describes the plague) and a thorough treatment of the contexts, see The Decameron Web [external link].