HIV & AIDS

Second HIV remission patient rekindles cure hope

For just the second time ever an HIV patient is in sustained remission from the virus in what was hailed by experts Tuesday as proof that the AIDS-causing condition could one day be curable.

Medical research

Deadly tick-borne virus cured with experimental flu drug, in mice

Only a few cases of the newly discovered Bourbon virus have been reported, and two of them ended in death, partly because no specific treatments are available for the tick-borne illness. Now, researchers at Washington University ...

Diseases, Conditions, Syndromes

Clues to building a better herpes vaccine

Efforts to develop an effective vaccine for genital herpes, a common sexually transmitted disease, have largely failed. In a new study published in Nature, Yale researchers explore why, and their findings could lead to a ...

Diseases, Conditions, Syndromes

A new picture of dengue's growing threat

Research published today in Nature Microbiology paints a startling new picture of where dengue, the world's fastest-growing mosquito-borne virus, will spread to put more than 6 billion people at risk toward the end of the ...

Diseases, Conditions, Syndromes

Stalk antibodies provide flu protection in humans

A universal flu vaccine that could prevent a potential influenza pandemic has been a holy grail for epidemiologists around the world ever since the first flu vaccines were developed in 1938.

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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