At least I believe that’s what you’re talking about. Though evidence of their existence was shown by both Ernest Hanbury Hankin while he was working with cholera (and trying to find anti-cholera agents) in the Ganges River basin in 1896, and Frederick Twort in 1915, the basics of virus structure and function were not definitively shown until nearly 1970, by Delbruk, Hershey, and Luria.
Phages infect and kill bacteria, and are highly specialized for each individual strain of bacteria. Despite their extreme specificity, one institute has taken up studying and producing “phage therapy" treatments since 1923 - the Tbilisi Institute in the country of Georgia. While phage therapy (or “biocontrol”) has proven highly effective in the studies done on it (there were some very large-scale studies done in the Soviet Union, and this isn’t just an alternative nonsense therapy), the very specific nature of phages, combined with the effort it takes to produce enough of them to use in a study, and the time it takes to test each bacterial strain to see which phage to use (often long enough for a patient to die - more than 24 hours for most bacteria), has led to very little testing outside of Georgia and other former Soviet countries.
But the continuing efficacy in the Tbilisi hospitals and Eliava Institute test subjects shows that there is promise for this sort of treatment, if nothing else works. If, for example, an extremely antibiotic-resistant staphylococcus appears (resistant to ALL known antibiotics), this may be the only opportunity to combat it once we produce an effective phage strain - we already know that the standard MRSA bacteria can be quickly eliminated with this virus.
Bacteriophages on an E. coli cell.
Plush bacteriophage! :D From GIANTmicrobes.
More on bacteriophages:
Animation of how the T4 Bacteriophage works
iBioSeminars: Bacteriophages: What are they?
TEDx: Applied Bacteriophage Therapy