One of the most serious threats of the medieval era was a plaque called "The Black Death". This term was related to the bubonic plaque
( pestilence, pest ), resulting from an infection with a bacterium called Yersinia pestis. Newer investigations of medical reports from
the 14th - 17th century questioned this definition, more probable reason seems to be a pandemia of a very aggressive ebola-like haemorrhagic fever.