Nature and Distribution of Viruses

Although several infectious diseases of animals and plants had been found to be caused by viruses during early 20^th century, the true nature of these ultra micros copic pathogens could not be investigated. All attempts to cultivate these in chemical culture media failed, and it was found that these can be cultivated only in cultures of live cells and tissues, ultimately, in1935 W.M. Stanley  achieved success in isolating and crystallizing tobacco  mosaic virus  (TMV)and shared the1946 Nobel Prize for  this work with Northrop and Summer who had earlier crystallized an enzyme for the first time. The crystals prepared by him were found to be viable infect ants, i.e. these were capable of infecting tobacco leaves as usual. Hence it was established that viruses are not organisms, but only nonliving inanimate or inert ultramicroscopic particles capable of infecting live cell l sand causing serious in factious diseases. These particles are now called various.

Invention of electron microscopy by knoll and Ruska (1934) just a year before Stanley work triggered a fast growth in our knowledge about viruses during the last 5-6decades under a separate branch of study, called virology.

Being inanimate and ultramicroscopic particles, viruses are innumerable and occur everywhere in soil, water and air upon earth.