The most popular theory of how the plague ended is through the implementation of quarantines. The uninfected would typically remain in their homes and only leave when it was necessary, while those who could afford to do so would leave the more densely populated areas and live in greater isolation.
Considering the severity of the Black Death, people less likely settled for 6-foot-rules and wearing a mask while waiting for their meal in an indoor restaurant. They probably were very serious about finding as much distance as they could from other human beings.
It also need to be mentioned that world population was far lower during that time, so population was far less dense. People could retrieve to their farms and live in self-sufficient isolation. Regardless of what variants popped up, they wouldn’t spread easily.
But did you know that the plague repeatedly returned to haunt Europe and the Mediterranean throughout the 14th to 17th centuries. According to Jean-Noël Biraben, the plague was present somewhere in Europe in every year between 1346 and 1671.
The third plague pandemic (1855–1859) started in China in the mid-19th century, spreading to all inhabited continents and killing 10 million people in India alone. The investigation of the pathogen that caused the 19th-century plague was begun by teams of scientists who visited Hong Kong in 1894, among whom was the French-Swiss bacteriologist Alexandre Yersin, after whom the pathogen was named.
Twelve plague outbreaks in Australia between 1900 and 1925 resulted in well over 1,000 deaths, chiefly in Sydney. This led to the establishment of a Public Health Department there which undertook some leading-edge research on plague transmission from rat fleas to humans via the bacillus Yersinia pestis.
The first North American plague epidemic was the San Francisco plague of 1900–1904, followed by another outbreak in 1907–1908.
A further outbreak in Madagascar was reported in November 2014. In October 2017 the deadliest outbreak of the plague in modern times hit Madagascar, killing 170 people and infecting thousands.
An estimate of the case fatality rate for the modern bubonic plague, following the introduction of antibiotics, is 11%, although it may be higher in underdeveloped regions.