History of virology

History of virology

1. MICROBIOLOGY QUICK LEARN
VIRUS- HISTORY
Saajida Sultaana Mahusook

2. •Virology is the study of viruses. Viruses have had enormous impact on humans and
other organisms, yet very little was known about their nature until fairly recently.
The concept of a virus as a distinct entity dates back to the late 1800s and their
existence became evident in the later 19th century, the infectious agents of numerous
diseases were being isolated and many infectious diseases had been proved to be
caused by bacteria. But there remained a large number of diseases for which no
bacterial cause could be established until it was realized that the responsible agents
were smaller than bacteria.

•Early in the 18th century, Lady Wortley Montagu, observed that Turkish women
inoculated their children against smallpox where the children came down with a mild
case but were subsequently immune.

•Later, Edward Jenner, stimulated by a girl‟s claim that she could not catch smallpox
because she had had cowpox, began inoculating humans with material from cowpox
lesions and published the results of 23 successful vaccinations in 1798. Although
Jenner did not understand the nature of smallpox, he successfully protected his
patients from the dreaded disease through exposure to the cowpox virus.

•The harmful agents were grouped together and sometimes called viruses [Latin:
virus, poison or venom]. Louis Pasteur used the term „virus‟ for any living infectious
disease agent.

3. •In 1884, the porcelain bacterial filter was developed by Charles
Chamberland, one of Pasteur‟s collaborators and inventor of the
autoclave, made possible the discovery of viruses. Tobacco mosaic
disease was the first to be studied with Chamberland‟s filter.

•In 1892, Dimitri Ivanowski showed that leaf extracts from infected
plants would induce tobacco mosaic disease even after filtration
removed all bacteria. He attributed this to the presence of a toxin.

•In 1898 and 1900, Martinus Beijerinck, published the results of
extensive studies on tobacco mosaic disease. As the filtered sap of
diseased plants was still infectious, he proposed that the disease was
caused by an entity different from bacteria, calling that a „filterable
virus‟. He observed that the virus would multiply only in living plant
cells, and could survive for long periods in a dried state.

•At the same time Friedrich Loeffler and Paul Frosch in Germany
found that the hoof-and-mouth disease of cattle was also caused by a
virus rather than by a toxin.

4. •In 1900, Walter Reed studied the yellow fever disease whose incidence had been
increasing in Cuba. Reed showed that yellow fever disease was due to a virus
transmitted by mosquitoes.

•By the early 20th century, it had been established that viruses were different from
bacteria and could cause diseases in plants, livestock, and humans.

•Shortly after the turn of the century, Vilhelm Ellermann and Oluf Bang in
Copenhagen reported that leukemia could be transmitted between chickens by
cell-free filtrates and was caused by a virus.

•In 1911, Peyton Rous reported that a virus (Rous sarcoma virus) was responsible
for a malignant muscle tumor in chickens. These studies established that some
malignancies are caused by viruses.

•In 1915, Frederick Twort reported that bacteria also could be attacked by viruses.
Twort isolated bacterial viruses that could attack and destroy micrococci and
intestinal bacilli.

5. •Felix d‟Herelle isolated bacterial viruses from patients with dysentery, caused by Shigella
dysenteriae. It was noted that when a virus suspension was spread on a layer of bacteria
growing on agar, clear circular areas containing viruses and lysed cells developed. A count of
these clear zones was used to estimate the number of viruses present. The procedure for
enumerating viruses is called plaque assay. He demonstrated that bacterial viruses could
reproduce only in live bacteria and named them bacteriophages (or phages) as they could eat
holes in bacterial “lawns.”

•The detailed morphology of viruses was studied by the invention of Electron microscope by
Ernst Ruska and Max Knoll in 1934.

•The chemical nature of viruses was established in 1935 when Wendell Stanley had
crystallized the tobacco mosaic virus (TMV) and found it to be largely or completely protein.

•The method of growing viruses on chick embryos was developed by Goodpasture in 1930‟s.
The use of living human and animal tissue cells for the in vitro culture of viruses was
developed by John Enders in 1949.

•Frederick Bawden and Norman Pirie managed to separate the TMV virus particles into
protein and nucleic acid making it clear that viruses are complexes of nucleic acids and
proteins able to reproduce only in living cells.

6. Reference
•Food Microbiology by Martin R. Adams and Maurice O. Moss,
3rd e.
•Food Microbiology by William C. Frazier and Dannis C.
Westhoff, 5th e.