Viruses are one of the most biologically diverse organisms. This result from the success viruses has had in parasitizing the realm of known living organisms. The understanding that viruses have the ability to rise and mutate to a level of a dangerous epidemic threat only began to surface in the past 100 years. The battle man has taken on against the viral world starts with the need to know your enemy.
With the first observations into the mechanistic nature of these, for the most part submicroscopic obligate intracellular parasites, has been recorded by an eighteenth century English doctor. E. Jenner noticed that milkmaids tended to catch a mild form of the "the pox". Jenner presumed it originated from the cows. After a brief healing time, the milkmaids were then protected against the more typical disfiguring ravages of smallpox. Probably an after effect of not being able to convince his colleagues, Jenner's observation went unexplained for nearly a century.3 Recorded observations such as this and living histories, like those of the BC Chinese that noticed that inhaling the dried crusts from smallpox lesions decreased their chance of infection,4 began man's effort to identify and challenge the enemy.
Fighting an enemy you cannot see is not necessarily the most effective challenge. For this, Antony van Leeuwen constructed the microscope from which he described the presence of "animalcules". However, not until Robert Hoch and Louis Pasteur jointly proposed, a century later, the "germ theory" of disease did these animalcules become significant.3,4 With tools of identification and methods of replication to follow, classification was the next logical step for the animalcules. .
With an amazing discovery by seemingly unlinked researchers, Beijerinck (whom was working on a disease that disfigured tobacco leaves) and the team of Loeffler and Frosch (whom were working on a foot-and-mouth disease of cattle) a massive distinction was made.