| Virology is the biological or medical study of viruses and viral diseases.
Virology is often thought of as being a very modern discipline, but people have been aware of and studying viral diseases for a long time. The first known record describing a viral disease is a 5700-year-old stone heiroglyph found in Memphis, Egypt that depicts a temple priest with paralytic poliomyelitis.
In pre-Christian times, the ancient Chinese learned how to innoculate people against smallpox by having them inhale scabs from smallpox victims. Western medicine would not discover this lifesaving procedure until thousands of years later when, on May 14, 1796, Edward Jenner successfully tried the same technique on a young boy.
Virology started getting going as a formalized science through the work of Louis Pasteur and Robert Koch in the mid-to-late 1800s. Pasteur worked extensively with rabies, which he called a "virus" after the Latin word for poison. Unfortunately, he was ultimately unable to distinguish between bacteria and viruses when it came to disease.
However, in 1892, a Russian botanist named Dmitri Iwanowski successfully isolated the virus that causes tobacco mosaic disease. He isolated the virus as clumps of crystal, which he then demonstrated could infect other tobacco plants.
In the 20th century, the development of laboratory techniques such as crystallography and spectroscopy made it possible for researchers to start figuring out the structure of viruses. The invention of the transmission electron microscope has made it possible for scientists to actually photograph viruses.
Virology has exploded as a field of study in the past century. Viruses are widely studied not only for the diseases they cause but because of the insights they can provide into the study of genetics and biotechnology.
References:
http://www-micro.msb.le.ac.uk/109/Introduction.html
http://medicine.wustl.edu/~virology/
http://www.stlcc.cc.mo.us/fp/users/kkiser/History.page.htm | 
