The virus is a biological infectious agent that reproduce inside any type of the living cells, the virus force the cell to produce thousands of copies. The virus consist of genes, molecules and protein coat. There are several types of viruses, some hit the plants, some hit the animals. Virus spread from a host to another by many ways that differ according to the virus.
Louis Pasteur (1822-1895) the famous French chemist and microbiologist, was the first to predict that there is a pathogen that is so small to be seen by the microscope. Then in the year 1884 Charles Chamberland (1851-1908) the French microbiologist invented a filter that was able to keep the bacteria as its pores were smaller than the bacteria. The filter was called Chamberland-Pasteur filter
In the year 1892, The Russian biologist Dmitry Ivanovsky (1864-1920) used Chamberland-Pasteur filter to study the tobacco mosaic virus.
In the year 1898, Martinus Beijerinck (1851-1931) the Dutch microbiologist, was able to assure that there is another source of infection other than the bacteria, he reached the first plant virus and called it contagium vivum fluidum.
Friedrich Loeffler (1852-1915) and Paul Frosch (1860-1928) the German bacteriologists, were able to discover the first animal virus Aphthovirus.
In the beginnings of the twentieth century, Frederick Twort (1877-1950) the English bacteriologist, discovered the virus that infect bacteria (bacteriophages). Félix d’Herelle (1873-1949) the French-Canadian microbiologist reached to the fact that when viruses added to bacteria, an area of dead bacteria is produced.
In the early years of the 20th century, scientists were able to produce viruses on animal tissues. As Ross Granville Harrison (1870 – 1959) the American biologist grew viruses in lymph in 1906. In the year 1913, the three scientists E. Steinhardt, C. Israeli, and R. A. Lambert reached for growing them on guinea pig corneal tissue. In 1928, H. B. Maitland and M. C. Maitland grew viruses on chicken kidneys. In the year 1931, Ernest William Goodpasture (1886-1960) an American pathologist and physician grew influenza and other viruses in fertilized chickens’ eggs. In the year 1949, John F. Enders (1897-1985), Thomas Weller (1915-2008), and Frederick Robbins (1916-2003) grew polio virus in cultured human embryo cells, and this later paved the way to Jonas Salk to reach the polio vaccine.
Starting from the second half of the 20th century thousands of types of viruses were discovered. In 1963 Baruch Blumberg (1925-2011) the American doctor discovered the hepatitis B virus, in 1981 the AIDS was discovered, then SARS was discovered in 2003.