A virus is a microscopic infectious agent that can reproduce only
inside a host cell. Viruses infect all types of organisms: from animals
and plants, to bacteria and archaea. Since the initial discovery of
tobacco mosaic virus by Martinus Beijerinck in 1898, more than 5,000
types of virus have been described in detail, although most types of
virus remain undiscovered. Viruses are ubiquitous, as they are found in
almost every ecosystem on Earth, and are the most abundant type of
biological entity on the planet. The study of viruses is known as
virology, and is a branch of microbiology. Viruses consist of two or
three parts: all viruses have genes made from either DNA or RNA, long
molecules that carry genetic information; all have a protein coat that
protects these genes; and some have an envelope of fat that surrounds
them when they are outside a cell. The origins of viruses in the
evolutionary history of life are unclear. Viruses spread in many ways;
plant viruses are often transmitted from plant to plant by insects that
feed on sap, such as aphids, while animal viruses can be carried by
blood-sucking insects. These disease-bearing organisms are known as
vectors. Not all viruses cause disease, as many viruses reproduce
without causing any obvious harm to the infected organism. Antiviral
drugs have been developed to treat both life-threatening and more minor
infections.
Read the rest of this article:
<http://en.wikipedia.org/wiki/Virus>
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Today's selected anniversaries:
869:
The Fourth Council of Constantinople, the eighth Catholic Ecumenical
Council, was convened to discuss the patriarchate of Photios I of
Constantinople.
<http://en.wikipedia.org/wiki/Fourth_Council_of_Constantinople_%28Roman_Catholic%29>
1877:
After battling the U.S. Army for more than three months, retreating
over 1,000 miles across Oregon, Washington, Idaho, and Montana, and
enduring a five-day siege, Chief Joseph and his Nez Perce band finally
surrendered.
<http://en.wikipedia.org/wiki/Chief_Joseph>
1903:
Samuel Griffith became the first Chief Justice of Australia, while
Edmund Barton and Richard O'Connor became the first Puisne Justices of
the High Court of Australia.
<http://en.wikipedia.org/wiki/Samuel_Griffith>
1948:
The International Union for Conservation of Nature was founded at a
congress sponsored by UNESCO director Julian Huxley in Fontainebleau,
France.
<http://en.wikipedia.org/wiki/International_Union_for_Conservation_of_Nature>
1986:
The British newspaper The Sunday Times published former nuclear
technician Mordechai Vanunu's story revealing details of Israel's
nuclear capability.
<http://en.wikipedia.org/wiki/Mordechai_Vanunu>
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Wiktionary's word of the day:
inure (v):
To cause to become accustomed to something unpleasant by prolonged
exposure
<http://en.wiktionary.org/wiki/inure>
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Wikiquote quote of the day:
Anyone who takes himself too seriously always runs the risk of looking
ridiculous; anyone who can consistently laugh at himself does not.
--Václav Havel
<http://en.wikiquote.org/wiki/V%C3%A1clav_Havel>
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