 Bacteriophages are the viruses that infect and replicate in bacteria.They were discovered in the early 20th century, by the English bacteriologist Frederick Twort (1877–1950).But before this time, in 1896, the bacteriologist Ernest Hanbury Hankin (1865–1939) reported that something in the waters of the River Ganges could kill "Vibrio cholerae" – the cause of cholera.