Syphilis
In 1905, two men named Fritz Schaudinn and Erich Hoffmann discovered that syphilis is caused by the Treponema pallidum bacteria. Five years later, Paul Ehrlich created the first treatment that helped treat syphilis (called Salvarsan). After that, scientists started to study penicillin. In 1943, it was officially decided that penicillin worked for syphilis.