Final answer:
The Black Death, a pandemic of the bubonic plague caused by the bacterium Yersinia pestis, killed about one-third of Europe's population between 1347 and 1350. Originating in Asia, it spread to Europe and caused profound mortality, societal and economic shifts, and a long-term population decline.
Step-by-step explanation:
The catastrophic event that killed about one-third of Europe's population between 1347 and 1350 was the Black Death, a devastating pandemic. The Black Death was an outbreak of the bubonic plague, caused by the bacterium Yersinia pestis. It is believed to have originated in Asia, spreading to Europe via trade routes such as the Silk Road, carried by fleas living on black rats. The mortality rate for the bubonic plague before the advent of antibiotics was extremely high, causing widespread death and societal upheaval.
Before it reached Europe, the disease had already wrought havoc in other parts of the world, including Asia and Africa, where it caused millions of deaths. The swift spread through European cities led to a severe population decline, from an estimated 450 million to about 350 to 375 million globally. The pandemic incited socio-economic changes as it weakened the feudal system, spurred peasant revolts, and led to a long period of population decline in Europe. Not until the fifteenth century did the population begin to recover.
Multiple outbreaks of the disease continued well into the 18th century, although none were as deadly as the initial wave. Despite the development of effective antibiotics that vastly reduced mortality rates, the bubonic plague still occurs, with 1,000 to 3,000 cases annually worldwide.