page_title: History of virology
section_title: Late 20th and early 21st century
hierarchical_section_title: History of virology / 20th century / Late 20th and early 21st century
caption_attribution_description: Computer assisted reconstruction of a rotavirus particle
context_page_description: The history of virology – the scientific study of viruses and the infections they cause – began in the closing years of the 19th century. Although Louis Pasteur and Edward Jenner developed the first vaccines to protect against viral infections, they did not know that viruses existed. The first evidence of the existence of viruses came from experiments with filters that had pores small enough to retain bacteria. In 1892, Dmitri Ivanovsky used one of these filters to show that sap from a diseased tobacco plant remained infectious to healthy tobacco plants despite having been filtered. Martinus Beijerinck called the filtered, infectious substance a "virus" and this discovery is considered to be the beginning of virology.
  The subsequent discovery and partial characterization of bacteriophages by Frederick Twort and Félix d'Herelle further catalyzed the field, and by the early 20th century many viruses had been discovered. In 1926, Thomas Milton Rivers defined viruses as obligate parasites. Viruses were demonstrated to be particles, rather than a fluid, by Wendell Meredith Stanley, and the invention of the electron microscope in 1931 allowed their complex structures to be visualised.
context_section_description: The second half of the 20th century was the golden age of virus discovery and most of the 2,000 recognised species of animal, plant, and bacterial viruses were discovered during these years. In 1946,  bovine virus diarrhea was discovered, which is still possibly the most common pathogen of cattle throughout the world and in 1957, equine arterivirus was discovered. In the 1950s, improvements in virus isolation and detection methods resulted in the discovery of several important human viruses including varicella zoster virus,  the  paramyxoviruses, – which include measles virus,  and respiratory syncytial virus –  and the rhinoviruses that cause the common cold. In the 1960s more viruses were discovered. In 1963, the hepatitis B virus was discovered by Baruch Blumberg (b. 1925). Reverse transcriptase, the key enzyme that retroviruses use to translate their RNA into DNA, was first described in 1970, independently by Howard  Temin and David Baltimore (b. 1938). This was important to the development of antiviral drugs – a key turning-point in the history of viral infections. In 1983, Luc Montagnier (b. 1932) and his team at the Pasteur Institute in France first isolated the retrovirus now called HIV. In 1989 Michael Houghton's team at Chiron Corporation discovered hepatitis C.
  New viruses and strains of viruses were discovered in every decade of the second half of the 20th century. These discoveries have continued in the 21st century as new viral diseases such as SARS and nipah virus have emerged. Despite scientists' achievements over the past one hundred years, viruses continue to pose new threats and challenges.
caption: A rotavirus particle
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