It has long been thought that the Black Death or The Plague killed half of the residents of Europe. But new research finds that mortality varied greatly by region.
The Black Death (1347–1352 AD) is the most infamous pandemic in human history. Advances in ancient DNA research have enabled researchers to identify the bacterium behind this terrible historical event
Source: Black Death Mortality Wasn’t as Widespread as Everyone Thinks | Ancient Origins
Regionally, The Plague was devastating but some areas indicate little, or no mortality based on this new investigation.
People are believed to have become sick after being bitten by fleas, which lived in association with rates, which themselves thrived on the garbage and filth of communities at the time. Once people were infected, the disease could also spread from person to person (possibly via fleas too), and quickly led to death in a matter of days.