Related topics: swine flu , flu , influenza , bird flu , flu virus
Virus
hideI: dsDNA viruses II: ssDNA viruses III: dsRNA viruses IV: (+)ssRNA viruses V: (−)ssRNA viruses VI: ssRNA-RT viruses VII: dsDNA-RT viruses
A virus (from the Latin virus meaning toxin or poison) 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. Viruses vary in shape from simple helical and icosahedral shapes, to more complex structures. They are about 1/100th the size of bacteria. The origins of viruses in the evolutionary history of life are unclear: some may have evolved from plasmids—pieces of DNA that can move between cells—while others may have evolved from bacteria. In evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity.
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. Influenza viruses are spread by coughing and sneezing, and others such as norovirus, are transmitted by the faecal-oral route, when they contaminate hands, food, or water. Rotaviruses are often spread by direct contact with infected children. HIV is one of several viruses that are transmitted through sexual contact.
Not all viruses cause disease, as many viruses reproduce without causing any obvious harm to the infected organism. Viruses such as hepatitis B can cause life-long or chronic infections, and the viruses continue to replicate in the body despite the hosts' defence mechanisms. In some cases, these chronic infections might be beneficial as they might increase the immune system's response against infection by other pathogens. However, in most cases viral infections in animals cause an immune response that eliminates the infecting virus. These immune responses can also be produced by vaccines that give lifelong immunity to a viral infection. Microorganisms such as bacteria also have defences against viral infection, such as restriction modification systems. Antibiotics have no effect on viruses, but antiviral drugs have been developed to treat both life-threatening and more minor infections.
For more information about Virus, read the full article at
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News tagged with virus
Researchers develop 'lab on a chip' that detects viruses (w/ Video)
Chemistry / Analytical Chemistry
23 hours ago |
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(PhysOrg.com) -- A team of Brigham Young University engineers and chemists has created an inexpensive silicon microchip that reliably detects viruses, even at low concentrations.
Infection-fighting antibodies made in plants as effective as costlier conventional version
Feb 08, 2010 |
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The first head-to-head comparison of therapeutic monoclonal antibodies produced from plants versus the same antibodies produced from mammalian cells has shown that plant-produced antibodies can fight infection equally well.
Is the US swine flu epidemic over?
Feb 05, 2010 |
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(AP) -- If the U.S. swine flu epidemic isn't over, it certainly looks as if it's on its last legs. While federal health officials are not ready to declare the threat has passed and the outbreak has run its ...
Scientists measure energy released from a virus during infection
Feb 05, 2010 |
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Within a virus's tiny exterior is a store of energy waiting to be unleashed. When the virus encounters a host cell, this pent-up energy is released, propelling the viral DNA into the cell and turning it into a virus factory. ...
Researcher to track spread of disease, malware and power outages
Feb 04, 2010 |
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An assistant professor with the Virginia Tech College of Engineering has won a $750,000 federal grant to formulate a mathematical framework that can track the spread of pandemics among populations and malware ...
Scientists find two compounds that lay the foundation for a new class of AIDS drug
Medicine & Health / HIV & AIDS
Feb 03, 2010 |
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A team of scientists at The Scripps Research Institute has identified two compounds that act on novel binding sites for an enzyme used by the human immunodeficiency virus (HIV), the virus that causes AIDS. The discovery lays ...
Chemists discover how antiviral drugs bind to and block flu virus
Feb 03, 2010 |
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Antiviral drugs block influenza A viruses from reproducing and spreading by attaching to a site within a proton channel necessary for the virus to infect healthy cells, according to a research project led ...
PNAS paper cites discovery of small RNA 'quality-control' mechanism
Feb 02, 2010 |
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(PhysOrg.com) -- When a person is exposed to a cold virus, whether he or she actually becomes ill may come down to how well short snippets of RNA in the person's defense response system interact with the RNA-based ...
Preventive program associated with reduced spread of H1N1 at summer camp
Feb 02, 2010 |
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A targeted program of preventive antiviral medication, combined with the use of hand sanitizers and surface decontamination, was associated with containing the spread of the H1N1 virus in a summer camp setting, according ...
Virus pulls bait and switch on insect vectors
Feb 01, 2010 |
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A common plant virus lures aphids to infected plants by making the plants more attractive, but when the insects taste the plant, they quickly leave for tastier, healthier ones. In the process, the insects ...
Tobacco plant-made therapeutic thwarts West Nile virus
Feb 01, 2010 |
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A new therapeutic made from tobacco plants has been shown to arrest West Nile virus infection, according to a new study by Arizona State University scientist Qiang Chen and his colleagues.
Of swine, birds and men -- pandemic H1N1 flu
Feb 01, 2010 |
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Current research suggests that pandemic H1N1 influenza of swine origin has distinct means of transmission from the seasonal flu, yet does not result in the pathogenic severity of avian flu viruses. The related report by ...
Compound found that targets wide range of viruses
Feb 01, 2010 |
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(PhysOrg.com) -- The compound was found to be effective against viruses that cause some of the world's deadliest diseases, such as AIDS, Ebola and Rift Valley fever.
Immune protein fends off exotic virus
Feb 01, 2010 |
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A study published online on February 1 in the Journal of Experimental Medicine shows that antiviral proteins called type I interferons (IFNs) are needed to fend off infection with an exotic mosquito-borne virus called Chikun ...
Virus-like particle vaccine protects monkeys from chikungunya virus
Jan 28, 2010 |
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(PhysOrg.com) -- An experimental vaccine developed using non-infectious virus-like particles (VLP) has protected macaques and mice against chikungunya virus, a mosquito-borne pathogen that has infected millions of people ...
