 He realised that he had discovered a new form of virus and later coined the term "bacteriophage".Between 1918 and 1921 d'Herelle discovered different types of bacteriophages that could infect several other species of bacteria including "Vibrio cholerae".Bacteriophages were heralded as a potential treatment for diseases such as typhoid and cholera, but their promise was forgotten with the development of penicillin.