Editing Virology (section)

==History==
{{Main|History of virology|Social history of viruses}}
[[File:Martinus Willem Beijerinck in his laboratory.jpg|thumb|right|alt=An old, bespectacled man wearing a suit and sitting at a bench by a large window. The bench is covered with small bottles and test tubes. On the wall behind him is a large old-fashioned clock below which are four small enclosed shelves on which sit many neatly labelled bottles.|[[Martinus Beijerinck]] in his laboratory in 1921]]
[[Louis Pasteur]] was unable to find a causative agent for [[rabies]] and speculated about a pathogen too small to be detected by microscopes.<ref>{{cite journal | vauthors = Bordenave G | title = Louis Pasteur (1822-1895) | journal = Microbes and Infection | volume = 5 | issue = 6 | pages = 553–60 | date = May 2003 | pmid = 12758285 | doi = 10.1016/S1286-4579(03)00075-3 }}</ref> In 1884, the French [[microbiologist]] [[Charles Chamberland]] invented the [[Chamberland filter]] (or Pasteur-Chamberland filter) with pores small enough to remove all bacteria from a solution passed through it.<ref>Shors pp. 74, 827</ref> In 1892, the Russian biologist [[Dmitri Ivanovsky]] used this filter to study what is now known as the [[tobacco mosaic virus]]: crushed leaf extracts from infected tobacco plants remained infectious even after filtration to remove bacteria. Ivanovsky suggested the infection might be caused by a [[toxin]] produced by bacteria, but he did not pursue the idea.<ref name="Collier3">Collier p. 3</ref> At the time it was thought that all infectious agents could be retained by filters and grown on a nutrient medium—this was part of the [[germ theory of disease]].<ref name="Dimmock">Dimmock p. 4</ref>

In 1898, the Dutch microbiologist [[Martinus Beijerinck]] repeated the experiments and became convinced that the filtered solution contained a new form of infectious agent.<ref>Dimmock pp. 4–5</ref> He observed that the agent multiplied only in cells that were dividing, but as his experiments did not show that it was made of particles, he called it a ''[[contagium vivum fluidum]]'' (soluble living germ) and reintroduced the word ''virus''. Beijerinck maintained that viruses were liquid in nature, a theory later discredited by [[Wendell Stanley]], who proved they were particulate.<ref name="Collier3" /> In the same year, [[Friedrich Loeffler]] and Paul Frosch passed the first animal virus, [[aphthovirus]] (the agent of [[foot-and-mouth disease]]), through a similar filter.<ref name="isbn0-12-375146-2">{{cite book | vauthors = Fenner F | veditors = Mahy BW, Van Regenmortal MH  |title=Desk Encyclopedia of General Virology |edition= 1|publisher=Academic Press |location=Oxford |year=2009 |page =  15|isbn=978-0-12-375146-1}}</ref>

In the early 20th century, the English bacteriologist [[Frederick Twort]] discovered a group of viruses that infect bacteria, now called [[bacteriophages]]<ref>Shors p. 827</ref> (or commonly 'phages'), and the French-Canadian microbiologist [[Félix d'Herelle]] described viruses that, when added to bacteria on an [[agar plate]], would produce areas of dead bacteria. He accurately diluted a suspension of these viruses and discovered that the highest dilutions (lowest virus concentrations), rather than killing all the bacteria, formed discrete areas of dead organisms. Counting these areas and multiplying by the dilution factor allowed him to calculate the number of viruses in the original suspension.<ref>{{cite journal | vauthors = D'Herelle F | title = On an invisible microbe antagonistic toward dysenteric bacilli: brief note by Mr. F. D'Herelle, presented by Mr. Roux. 1917 | journal = Research in Microbiology | volume = 158 | issue = 7 | pages = 553–54 | date = September 2007 | pmid = 17855060 | doi = 10.1016/j.resmic.2007.07.005 | doi-access = free }}</ref> Phages were heralded as a potential treatment for diseases such as [[typhoid]] and [[cholera]], but their promise was forgotten with the development of [[penicillin]]. The development of [[Antimicrobial resistance|bacterial resistance to antibiotics]] has renewed interest in the therapeutic use of bacteriophages.<ref name="pmid26891965">{{cite journal | vauthors = Domingo-Calap P, Georgel P, Bahram S | title = Back to the future: bacteriophages as promising therapeutic tools | journal = HLA | volume = 87 | issue = 3 | pages = 133–40 | date = March 2016 | pmid = 26891965 | doi = 10.1111/tan.12742 | s2cid = 29223662 }}</ref>

By the end of the 19th century, viruses were defined in terms of their [[infectivity]], their ability to pass filters, and their requirement for living hosts. Viruses had been grown only in plants and animals. In 1906 [[Ross Granville Harrison]] invented a method for [[tissue culture|growing tissue]] in [[lymph]], and in 1913 E.&nbsp;Steinhardt, C.&nbsp;Israeli, and R.A. Lambert used this method to grow [[vaccinia]] virus in fragments of guinea pig corneal tissue.<ref>{{cite journal| vauthors = Steinhardt E, Israeli C, Lambert RA |year = 1913|title = Studies on the cultivation of the virus of vaccinia|journal = The Journal of Infectious Diseases |volume = 13|pages = 294–300|doi = 10.1093/infdis/13.2.294|issue = 2|url = https://zenodo.org/record/1431761}}</ref> In 1928, H. B. Maitland and M. C. Maitland grew vaccinia virus in suspensions of minced hens' kidneys. Their method was not widely adopted until the 1950s when [[poliovirus]] was grown on a large scale for vaccine production.<ref>Collier p. 4</ref>

Another breakthrough came in 1931 when the American pathologist [[Ernest William Goodpasture]] and [[Alice Miles Woodruff]] grew influenza and several other viruses in fertilised chicken eggs.<ref>{{cite journal | vauthors = Goodpasture EW, Woodruff AM, Buddingh GJ | title = The cultivation of vaccine and other viruses in the chorioallantoic membrane of chick embryos | journal = Science | volume = 74 | issue = 1919 | pages = 371–72 | date = October 1931 | pmid = 17810781 | doi = 10.1126/science.74.1919.371 | bibcode = 1931Sci....74..371G }}</ref> In 1949, [[John Franklin Enders]], [[Thomas Huckle Weller|Thomas Weller]], and [[Frederick Robbins]] grew poliovirus in cultured cells from aborted human embryonic tissue,<ref name="WellerLibrary2004">{{cite book|author=Thomas Huckle Weller|title=Growing Pathogens in Tissue Cultures: Fifty Years in Academic Tropical Medicine, Pediatrics, and Virology|url=https://books.google.com/books?id=jYbqLuOVJlEC&pg=PA57|year=2004|publisher=Boston Medical Library|isbn=978-0-88135-380-8|page=57}}</ref> the first virus to be grown without using solid animal tissue or eggs. This work enabled [[Hilary Koprowski]], and then [[Jonas Salk]], to make an effective [[polio vaccine]].<ref>{{cite journal | vauthors = Rosen FS | title = Isolation of poliovirus--John Enders and the Nobel Prize | journal = The New England Journal of Medicine | volume = 351 | issue = 15 | pages = 1481–83 | date = October 2004 | pmid = 15470207 | doi = 10.1056/NEJMp048202 }}</ref>

The first images of viruses were obtained upon the invention of [[electron microscopy]] in 1931 by the German engineers [[Ernst Ruska]] and [[Max Knoll]].<ref>{{cite book | title = Nobel Lectures, Physics 1981–1990 | date = 1993 | veditors = Frängsmyr T, Ekspång G | publisher = World Scientific Publishing Co. | location = Singapore | bibcode = 1993nlp..book.....F }}
* In 1887, Buist visualised one of the largest, Vaccinia virus, by optical microscopy after staining it. Vaccinia was not known to be a virus at that time. (Buist J.B. ''Vaccinia and Variola: a study of their life history'' Churchill, London)</ref> In 1935, American biochemist and virologist [[Wendell Meredith Stanley]] examined the tobacco mosaic virus and found it was mostly made of protein.<ref>{{cite journal | vauthors = Stanley WM, Loring HS | title = The Isolation of Crystalline Tobacco Mosaic Virus Protein From Diseased Tomato Plants | journal = Science | volume = 83 | issue = 2143 | pages = 85 | date = January 1936 | pmid = 17756690 | doi = 10.1126/science.83.2143.85 | bibcode = 1936Sci....83...85S }}</ref> A short time later, this virus was separated into protein and RNA parts.<ref>{{cite journal | vauthors = Stanley WM, Lauffer MA | title = Disintegration of Tobacco Mosaic Virus in Urea Solutions | journal = Science | volume = 89 | issue = 2311 | pages = 345–47 | date = April 1939 | pmid = 17788438 | doi = 10.1126/science.89.2311.345 | bibcode = 1939Sci....89..345S }}</ref>
The tobacco mosaic virus was the first to be [[crystal]]lised and its structure could, therefore, be elucidated in detail. The first [[X-ray diffraction]] pictures of the crystallised virus were obtained by Bernal and Fankuchen in 1941. Based on her X-ray crystallographic pictures, [[Rosalind Franklin]] discovered the full structure of the virus in 1955.<ref name="pmid18702397">{{cite journal | vauthors = Creager AN, Morgan GJ | title = After the double helix: Rosalind Franklin's research on Tobacco mosaic virus | journal = Isis | volume = 99 | issue = 2 | pages = 239–72 | date = June 2008 | pmid = 18702397 | doi = 10.1086/588626 | s2cid = 25741967 }}</ref> In the same year, [[Heinz Fraenkel-Conrat]] and [[Robley Williams]] showed that purified tobacco mosaic virus RNA and its protein coat can assemble by themselves to form functional viruses, suggesting that this simple mechanism was probably the means through which viruses were created within their host cells.<ref>Dimmock p. 12</ref>

The second half of the 20th century was the golden age of virus discovery, and most of the documented species of animal, plant, and bacterial viruses were discovered during these years.<ref name="pmid18446425">{{cite journal | vauthors = Norrby E | s2cid = 10595263 | title = Nobel Prizes and the emerging virus concept | journal = Archives of Virology | volume = 153 | issue = 6 | pages = 1109–23 | year = 2008 | pmid = 18446425 | doi = 10.1007/s00705-008-0088-8 }}</ref> In 1957 [[Arterivirus|equine arterivirus]] and the cause of [[Bovine virus diarrhea|bovine virus diarrhoea]] (a [[pestivirus]]) were discovered. In 1963 the [[Hepatitis B|hepatitis B virus]] was discovered by [[Baruch Blumberg]],<ref>Collier p. 745</ref> and in 1965 [[Howard Temin]] described the first [[retrovirus]]. [[Reverse transcriptase]], the [[enzyme]] that retroviruses use to make DNA copies of their RNA, was first described in 1970 by Temin and [[David Baltimore]] independently.<ref name="pmid4348509">{{cite journal | vauthors = Temin HM, Baltimore D | title = RNA-directed DNA synthesis and RNA tumor viruses | journal = Advances in Virus Research | volume = 17 | pages = 129–86 | year = 1972 | pmid = 4348509 | doi = 10.1016/S0065-3527(08)60749-6 | isbn = 9780120398171 }}</ref> In 1983 [[Luc Montagnier]]'s team at the [[Pasteur Institute]] in France, first isolated the retrovirus now called HIV.<ref name="Barre">{{cite journal | vauthors = Barré-Sinoussi F, Chermann JC, Rey F, Nugeyre MT, Chamaret S, Gruest J, Dauguet C, Axler-Blin C, Vézinet-Brun F, Rouzioux C, Rozenbaum W, Montagnier L | display-authors = 6 | title = Isolation of a T-lymphotropic retrovirus from a patient at risk for acquired immune deficiency syndrome (AIDS) | journal = Science | volume = 220 | issue = 4599 | pages = 868–71 | date = May 1983 | pmid = 6189183 | doi = 10.1126/science.6189183 | bibcode = 1983Sci...220..868B }}</ref> In 1989 [[Michael Houghton (virologist)|Michael Houghton]]'s team at [[Chiron Corporation]] discovered [[hepatitis C]].<ref name="choo">{{cite journal | vauthors = Choo QL, Kuo G, Weiner AJ, Overby LR, Bradley DW, Houghton M | title = Isolation of a cDNA clone derived from a blood-borne non-A, non-B viral hepatitis genome | journal = Science | volume = 244 | issue = 4902 | pages = 359–62 | date = April 1989 | pmid = 2523562 | doi = 10.1126/science.2523562 | citeseerx = 10.1.1.469.3592 | bibcode = 1989Sci...244..359C }}</ref><ref name="pmid19781804">{{cite journal | vauthors = Houghton M | title = The long and winding road leading to the identification of the hepatitis C virus | journal = Journal of Hepatology | volume = 51 | issue = 5 | pages = 939–48 | date = November 2009 | pmid = 19781804 | doi = 10.1016/j.jhep.2009.08.004 | url = http://www.journal-of-hepatology.eu/article/S0168-8278%2809%2900535-2/fulltext | doi-access = free }}</ref>