The word virus was first used to describe an agent that causes infectious disease by Edward Jenner...you know, the small pox guy. The first person to identify a virus as distinct from bacteria and other cellular life was probably Dmitri Ivanoski, who filtered tobacco extracts that had tobacco mosaic disease—caused by tobacco mosaic virus—and found that he could spread disease through these filtered extracts. Martinus Beijerinck did Dmitri one better by passaging the filtered extract again and again, proving that the filtered extract was actually growing and replicating in each plant. It was not simply a toxin.
Chicken Sarcoma (must…tear…chicken...apart)
In 1911, Peyton Rous discovered that a virus caused cancer in chickens, or a chicken sarcoma, and he was the first to show that viruses caused cancer. The virus he discovered, Rous sarcoma virus, was a retrovirus.
Since the discovery of viruses as infectious, disease-causing agents, they have been a useful tool to understand the biology of bacteria and eukaryotic cells. Because viruses need to hijack the host cell, they can be used to understand the functions of certain proteins in a cell. The following discoveries originated from virus research.
Therefore, virus research is not only important to understanding how viruses infect us, but it is also important for getting at our own biology through its disruption during a virus infection.