The Tobacco Mosaic "Virus" is said to be the first "virus" ever discovered. The particle has even been purified and biochemically characterised.
References:
1. “Tobacco Mosaic Virus,” in Encyclopedia of Virology (Third Edition), 2008:
2. “One Hundred Years of Virology,” Journal of Virology, 1992:
3. “Soviet Studies On Viruses,” Science, 1944:
4. “Isolation and Properties of TM and other Virus Proteins,” W Stanley, 1938:
5. “Isolation of crystalline tobacco Mosaic Virus Protein from Tomato Plants,” The Journal of Biological Chemistry, 1937: Vol 117.
6. WISSENSCHAFFTPLUS magazin 4/2020:
7. Tobacco Diseases and Decay” by Frederick Wolf, 1935.
8. “Concerning a Contagium Vivum Fluidum as cause of the Spot Disease of tobacco leaves,” 1898:
9. “Über die Mosaikkrankheit der Tabakspflanze,” 1903:
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