Daniila Samoilovich, Russian epidemiologist.
Daniila Samoilovich was born in 1742. He graduated from Saint Petersburg (university, college of medicine??), the then capital of Russia in the time of Catherine the Great. After this, he worked hard as a doctor and in 1768 he set out for the Russian-Turkish war front.
There he became an epidemiologist. He put a lot of effort into reducing the incidence of disease in the army. And he achieved this purpose successfully.
It was then that he encountered the plague. He knew four languages: Latin, Polish, French and of course Russian, but due to the need to communicate with locals, he learned Moldavian.
Then he figured out that the plague was transmitted not through the air, but through the infected materials? (deceased = dead) stuff. Because of their misconceptions, people performed some crazy actions to protect against the disease, such as cutting a trees, shooting a cannon, or ringing bells. They had the belief that this help the air to move.
He worked so hard he became ill, but the order for his relocation back was delayed for a few months. Instead of the relocation to a calm place, he was sent straight to Moscow, where the plague epidemic was raging and which achieved its peak that year, 1771.
But that is another story about the heroism of Russian medics.