How did the germ theory of disease improve the understanding of plague?

The germ theory of disease revolutionized the understanding of plague by shifting the medical consensus away from the erroneous belief that the disease was caused by "poisonous miasma" or vapors. Instead, it established that plague is caused by a specific microorganism, the bacterium Yersinia pestis.12

This scientific framework enabled several critical advancements:

• Identification: In 1894, researchers Alexandre Yersin and Kitasato Shibasaburo independently isolated the bacterium, proving it was the causative agent of plague through laboratory experiments.21
• Transmission: Building on this knowledge, Paul-Louis Simond demonstrated that the bacterium is transmitted to humans by fleas carried by rodents, replacing earlier misconceptions about how the disease spread.21
• Treatment and Prevention: The germ theory facilitated the development of vaccines and, eventually, antibiotics such as streptomycin, which directly target the pathogen.231

These breakthroughs transformed plague from a mysterious, uncontrollable "pestilential fever" into a treatable and preventable condition, leading to the implementation of effective public health measures like rat-proofing and sanitation.231