1096-1099: Internal Fires at Nivers
It is said that in Library 5 of Albert Krantz's Historia Saxonica ("Saxon History," published 1520), he tells of a strange disease reported in a place called either Niverva, Nivers, or Nineruam during the time of Godfrey of Bologne's "Christian war." It was said that people there "were burning of invisible fire in their entrails," and that some people cut off a foot or a hand where the burning began to prevent it from spreading further.
Dating the Matter
"Godfrey of Bologne" likely refers to Godfrey of Bouillon [c. 1060–1100], who was son of Eustace II, Count of Boulogne. Godfrey was one of the leaders of the First Crusade to free Jerusalem from 1096, and ruled Jerusalem from 1099 until his death... so the reference to his "Christian War" likely narrows our time frame down to between 1096 and 1099 for the report of the above, assuming it’s true. I have been unable to determine where "Niverva," "Nivers," or "Nineruam" would have been.