When did people realize that microbes cause disease?

1675-1683: Antonie van Leeuwenhoek Observes Microorganisms

- Using the microscope he himself built, the Dutch scientist Antonie van Leeuwenhoek observed and sketched "animalcules" in pond water, rainwater, saliva, feces, and other samples, becoming one of the first to observe microorganisms.

1796: Edward Jenner's Vaccination Experiments

- English physician Edward Jenner noticed that milkmaids who were exposed to cowpox, a mild disease, were somehow protected from contracting the more severe smallpox.

Using cowpox blisters, he successfully vaccinated a young boy against smallpox, demonstrating the principle of vaccination.

1847: Ignaz Semmelweis and Puerperal Fever

- Hungarian physician Ignaz Semmelweis reduced childbed fever mortality to nearly zero by enforcing strict hand-washing protocols for medical staff in maternity wards, suggesting that unseen contaminants on the hands of healthcare professionals caused infections.

1857-1862: Louis Pasteur's Germ Theory of Fermentation and Disease

- French scientist Louis Pasteur conducted a series of experiments showing that microorganisms caused fermentation and that the growth of microorganisms could be inhibited by heating. He proposed that infections are caused by specific organisms rather than spontaneous generation.

1867-1876: Joseph Lister's Antiseptic Surgery

- Drawing on Pasteur's work, British surgeon Joseph Lister introduced antiseptic techniques to prevent infections during surgical procedures. His methods significantly reduced post-operative infections and surgical mortality rates.

1876-1884: Robert Koch's Postulates and Pure Culture Techniques

- German physician Robert Koch developed a set of criteria, known as Koch's postulates, to establish the causal relationship between specific microorganisms and specific diseases. He also pioneered pure culture techniques to isolate and study specific bacteria and their infectious properties.

1928: Alexander Fleming and Penicillin

- While working on the influenza virus, Scottish biologist Alexander Fleming accidentally discovered that the mold Penicillium notatum produced a substance that could kill bacteria. This finding paved the way for the development of penicillin and other antibiotics.