The pneumonic form of plague (bacterial infection), also known as the Black Death (1347-51), killed around a quarter of the population of Europe, and some 75 million worldwide.  

Estimates based on local archives suggest that between one-eighth and two-thirds of the affected population died of the disease.  Contemporary French historian Jean Froissart (1333-1419) believed that about one-third of the population of Europe-some 25 million people-succumbed in the first epidemic, an estimate which is now widely accepted by scientists and historians.

The disease still affects 1,000 to 3,000 people a year, but can now be cured.