Virology

Virology is the scientific study of viruses: their structure, classification, evolution, and the ways they infect and replicate inside host cells. The field traces to the 1890s, when researchers investigating tobacco mosaic disease in plants found an infectious agent that passed through filters fine enough to remove every known bacterium, proof of a pathogen smaller than any microbe then recognized. Dmitri Ivanovsky observed this filterable agent in 1892 but took it for a bacterial toxin; Martinus Beijerinck repeated the experiment independently in 1898, recognized the agent as a new, self-replicating class of infectious matter, and coined the word virus. For decades a virus was understood only as an infectious fluid, until Wendell Stanley crystallized tobacco mosaic virus in 1935 and showed it behaved as a definable chemical particle, work that shared the 1946 Nobel Prize in Chemistry and tied virology to biochemistry. Peyton Rous's 1910 discovery that a filterable agent could transmit cancer in chickens, largely dismissed for decades, was eventually recognized with the 1966 Nobel Prize in Physiology or Medicine, the longest gap between a discovery and its Nobel recognition in the prize's history. Virology organized as a discipline distinct from general microbiology only in the second half of the twentieth century, and today spans plant, animal, human and microbial viruses, using electron microscopy and genome sequencing as core tools.