The number is not really known. Estimates for the Black Death, the outbreak of the Bubonic Plague in 1347-1352, run from 75 million to 200 million deaths. There were many other outbreaks, which added to this number.
"The deadly disease has claimed nearly 200 million lives (although there is some debate as to whether all of the plagues attributed to it are in fact the same disease)." (from Wikipedia article on the Bubonic Plague)
There are links below to the sections of articles on the Black Death and the Bubonic Plague that deal with the numbers of people who died.
the bubonic plague, spread by rats bitten bye infected fleas
the Bubonic Plague occurred in Europe about 400 years ago
The bubonic plague started in Asia and spread to Europe.
1/3 of people died in Europe.
the bubonic plague
The Bubonic Plague killed millions of people.
Europe
The biggest bubonic plague breakout in history was The Black Death, which infected Central Asia, Egypt, & parts of Europe. The plague killed over 25 million people in Europe alone! That's a third of Europe's population!
Europe
Europe
Bubonic Plague
Rats and fleas carried the disease and spread it to the people of Europe.