Related topics: bacteria · influenza · immune system · protein · virus

Atomic structures mapped in measles, mumps, flu and RSV

Northwestern University researchers have, for the first time, determined the 3-D atomic structure of a key complex in paramyxoviruses, a family of viruses that includes measles, mumps, human parainfluenza and respiratory ...

New pathogenic mechanism for influenza NS1 protein found

Influenza is a deadly virus, with about 290,000 to 650,000 deaths worldwide each year. When pandemics hit, the toll can soar: The Spanish flu of 1918 caused 40 million to 50 million deaths, the Asian flu of 1957 caused 2 ...

Cryo-electron microscopy opens a door to fight Epstein-Barr

The Epstein-Barr virus is one of the most widespread human viruses. Part of the herpesvirus family, it causes glandular fever (infectious mononucleosis), cancer and autoimmune diseases. At present, there is no treatment for ...

Researchers identify new 'universal' target for antiviral treatment

As the coronavirus outbreak shows, viruses are a constant threat to humanity. Vaccines are regularly developed and deployed against specific viruses, but that process takes a lot of time, doesn't help everyone who needs protection, ...

Viruses reprogram cells into different virocells

If it looks like a duck and quacks like a duck, so the adage goes, it must be a duck. But if the duck gets infected by a virus so that it no longer looks or quacks like one, is it still a duck? For a team led by researchers ...

The invasive Argentine ant has seasonal viruses

Argentine ants are one of the most successful invasive species in the world. Scientist from University of Oulu and University of Girona, Spain, have previously identified viruses from the invasive Argentine ants of the Mediterranean ...

France keeps eyes peeled for ruinous tomato virus

France's agriculture ministry said Thursday that it was increasing surveillance of fields to stave off a ruinous virus affecting tomatoes that has already been found in neighbouring countries.

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Virus

I: 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.

This text uses material from Wikipedia, licensed under CC BY-SA