ccording to the primary source, many people thought that the Jews infected wells and so caused the plague. Was this a fact or opinion?

Based on the information provided, it can be inferred that the claim that "Jews infected wells and caused the plague" was an opinion held by many people at that time. It is important to note that this belief was a result of widespread anti-Semitic sentiment during the period of the plague. However, it is essential to emphasize that this belief is not supported by any factual evidence and has been thoroughly debunked by historical research.