Wasn’t the plague carried by a rat? A story for our times, with apologies to historians:
One summer a long time ago on an island near Europe, the people were getting sick. Not everyone was sick at once. Some were genetically predisposed never to be sick, and they of course prospered. Those who were sick that summer weren’t numerous enough to be noticed.
And so it went on, for a number of summers people got sick and died, but the winter came and no-one noticed. Then one summer many people became sick (but not all) and many died.
It seemed nothing could be done, but the people suspected it was the rat.
Unbeknownst to the people, the rat had a disease that was transmitted by the many fleas which lived on the rat. By this time it was all too late. There was no Pied Piper and the rat wouldn’t go by itself.
Then what appeared to be a small accident started a fire. For many this seemed to be another calamity. Many of the old structures were destroyed and disappeared. Things appeared worse.
The people rallied and the old structures were replaced by new and better structures.
Best of all, the people discovered the rat was gone and so was the plague.