People forget that germ theory only gained prominence at the end of the 19th century. Before that people couldn't comprehend how something so tiny that it's invisible to the naked eye could kill you. Doctors were insulted by the idea that they could spread disease. Even when Semmelweis had data showing lower death rates, he was resisted and was driven out of the profession.
It was Antonie van Leeuwenhoek's invention of the microscope, and his subsequent discovery of what he dubbed "animalcules," that changed human perception of infectious disease forever. When I was a kid, one of my books was "Pioneer Germ Fighters," I'd recommend it to anyone who is interested in teaching the history of Immunology to their kids. Or learning it themselves for that matter. It's never too late to learn stuff.
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