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How did Louis Pasteur and Robert Koch contribute to understanding infectious diseases?

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Tuberculosis — disease A doctor examining chest X-rays of patients infected with tuberculosis, which remains one of the world's deadliest diseases.

Louis Pasteur and Robert Koch were instrumental in establishing the germ theory of disease, which revolutionized pathology by proving that specific microorganisms cause infectious diseases.12

Louis Pasteur
Pasteur provided the foundational evidence for germ theory by disproving spontaneous generation through his swan-neck flask experiments, demonstrating that microorganisms are present in the environment and do not arise from dead matter. His work on fermentation established that specific microbes cause specific processes, a principle he extended to human and animal diseases. He also pioneered vaccination techniques, developing vaccines for anthrax, chicken cholera, and rabies.321

Robert Koch
Koch advanced bacteriology by developing rigorous laboratory methods to isolate, cultivate, and study bacteria. He is best known for establishing Koch’s postulates, a set of criteria used to confirm that a specific microorganism is the causative agent of a particular disease. His meticulous investigations led to the identification of the bacteria responsible for tuberculosis and cholera.145