Abstract
Viral infections have been recorded unknowingly from the beginning of recorded history. The ancient Greeks and Romans described plagues of unknown origin. In general, infections were blamed on sins and punishment, balances of “vital humors” or on “miasma,” (rotten smells). In the sixteenth century, Girolamo Fracastoro suggested that infectious agents might spread disease, as did Agostino Bassi, studying diseases of silkworms. The development of the microscope by Hook and Van Leeuwenhoek in the seventeenth century led to the discovery of a new living world inhabited by very small creatures. Edward Jenner in England demonstrated that smallpox, a dreaded disease, could be prevented by inoculation with an organism that caused pockmarks on cows and dairymaids; this was the beginning of the concept of vaccination. Louis Pasteur proved that fermentation only occurred in the presence of air and was due to microorganisms. Pasteur and Pierre Roux, a colleague, as well as Jacob Henle and Robert Koch, proved that germs caused bacterial diseases such as anthrax and tuberculosis; Pasteur and Roux developed a vaccine against rabies by passaging the infectious material through rabbits. By the end of the nineteenth century it had been established that most infectious diseases were the result of germs. In parallel with this research, plant scientists had isolated material that passed through a low pore filter that was infectious to tobacco plants. This was called a “virus,” from the Latin for poison. Viruses were also found to be associated with leukemia and other cancers of chickens. The twentieth century saw the discovery of bacteriophage, viruses that attack bacteria, and the use of such bacteriophage to launch studies of molecular biology, and DNA and RNA structure.