Related topics: proceedings of the national academy of sciences , cells , hiv , bird flu , h5n1
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
Biological catch-22 prevents induction of antibodies that block HIV
Medicine & Health / HIV & AIDS
8 hours ago |
5 / 5 (1) |
1
Scientists seeking to understand how to make an AIDS vaccine have found the cause of a major roadblock. It turns out that the immune system can indeed produce cells with the potential to manufacture powerful HIV-blocking ...
The global dynamics and spread of Hepatitis C virus 1a and 1b: A phylogeographical analysis
6 hours ago |
not rated yet |
0
Research published this week in PLoS Medicine finds that the global spread of Hepatitis C virus (HCV) coincided with widespread use of transfused blood and with the expansion of intravenous drug use but slowed before wholes ...
New insight into selective binding properties of infectious HIV
Medicine & Health / HIV & AIDS
8 hours ago |
not rated yet |
0
Free infectious HIV-1 is widely thought to be the major form of the virus in the blood of infected persons. U.S. Military HIV Research Program (MHRP) researchers, however, have demonstrated that essentially all of the infectious ...
Study reveals H1N1 unexpected weakness
Dec 10, 2009 |
4.8 / 5 (19) |
7
The H1N1 influenza virus has been keeping a secret that may be the key to defeating it and other flu viruses as well.
Research reveals further progress toward AIDS vaccine
Medicine & Health / HIV & AIDS
Dec 14, 2009 |
1 / 5 (1) |
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(PHILADELPHIA) Researchers from Thomas Jefferson University are one step closer to developing a vaccine against the AIDS disease.
New giant virus discovered
Dec 09, 2009 |
4.3 / 5 (18) |
8
Scientists in France have isolated a new giant virus that lurks inside amoeba and whose gene pool includes genetic material from other species.
Math goes viral: Researchers make math and science real for high-school students
Other Sciences / Social Sciences
Dec 14, 2009 |
5 / 5 (1) |
0
At least a dozen Alberta high-school calculus classrooms were exposed to the West Nile virus recently.
Scientists use virus to kill cancer cells while leaving normal cells intact
Dec 03, 2009 |
5 / 5 (7) |
3
(PhysOrg.com) -- A virus that in nature infects only rabbits could become a cancer-fighting tool for humans. Myxoma virus kills cancerous blood-precursor cells in human bone marrow while sparing normal blood stem cells, a ...
H1N1 influenza adopted novel strategy to move from birds to humans
Dec 08, 2009 |
5 / 5 (2) |
1
(PhysOrg.com) -- The 2009 H1N1 influenza virus used a new strategy to cross from birds into humans, a warning that it has more than one trick up its sleeve to jump the species barrier and become virulent.
Gene Hijacked By HIV Ancestor Suggests New Way to Block Viral Reproduction
Dec 07, 2009 |
4.9 / 5 (7) |
0
(PhysOrg.com) -- An ancestor of the AIDS virus hijacked an entire gene, perhaps from some prehistoric cat it had infected, a gene that makes it much better able to infect humans, according to a study published ...
Tumor-attacking virus strikes with 'one-two punch'
Dec 01, 2009 |
5 / 5 (6) |
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Ohio State University cancer researchers have developed a tumor-attacking virus that both kills brain-tumor cells and blocks the growth of new tumor blood vessels.
Scientists reveal key structure from ebola virus
Dec 08, 2009 |
5 / 5 (2) |
0
Scientists at The Scripps Research Institute have determined the structure of a critical protein from the Ebola virus, which, though rare, is one of the deadliest viruses on the planet killing between 50 and 90 percent of ...
Severity of H1N1 flu in US during current flu season may be less than feared
Dec 08, 2009 |
not rated yet |
1
A new study from researchers at the UK Medical Research Council and the Harvard School of Public Health (HSPH) projects that the severity of the H1N1 flu during the autumn-winter flu season in the U.S. will likely be less ...
West Nile virus infection may persist in kidneys years after initial infection
Dec 07, 2009 |
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A new study shows that people who have been infected with West Nile virus may have persistent virus in their kidneys for years after initial infection, potentially leading to kidney problems. The research, which appears in ...
Defects in T cells make West Nile virus more deadly in older adults
Dec 04, 2009 |
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0
(PhysOrg.com) -- West Nile virus is more deadly in older adults due to defects in T cells, according to a study conducted by researchers from the UA College of Medicine.
