Portal:Viruses
The Viruses Portal
Welcome!
Viruses are small infectious agents that can replicate only inside the living cells of an organism. Viruses infect all forms of life, including animals, plants, fungi, bacteria and archaea. They are found in almost every ecosystem on Earth and are the most abundant type of biological entity, with millions of different types, although only about 6,000 viruses have been described in detail. Some viruses cause disease in humans, and others are responsible for economically important diseases of livestock and crops.
Virus particles (known as virions) consist of genetic material, which can be either DNA or RNA, wrapped in a protein coat called the capsid; some viruses also have an outer lipid envelope. The capsid can take simple helical or icosahedral forms, or more complex structures. The average virus is about 1/100 the size of the average bacterium, and most are too small to be seen directly with an optical microscope.
The origins of viruses are unclear: some may have evolved from plasmids, others from bacteria. Viruses are sometimes considered to be a life form, because they carry genetic material, reproduce and evolve through natural selection. However they lack key characteristics (such as cell structure) that are generally considered necessary to count as life. Because they possess some but not all such qualities, viruses have been described as "organisms at the edge of life".
Selected disease
.jpg)
Myxomatosis is a disease of rabbits caused by Myxoma virus, a poxvirus in the genus Leporipoxvirus. The natural hosts are brush rabbits (Sylvilagus bachmani) in North America and tapeti (S. brasiliensis) in South and Central America, in which the myxoma virus causes only a mild disease, involving skin nodules. In European rabbits (Oryctolagus cuniculus), it causes a severe, often fatal, disease. Symptoms include fever, swelling of the eyelids and anogenital area, a mucopurulent ocular and nasal discharge, respiratory distress and hypothermia. Death generally occurs 10–12 days after infection. Myxoma virus is transmitted passively (without replication) by arthropod vectors, usually via the bites of mosquitoes and fleas, and also mites, flies and lice. It can also be transmitted by direct contact, and is shed in the ocular and nasal discharge and from eroded skin.
Myxoma virus was intentionally introduced in Australia, France and Chile in the 1950s to control wild European rabbit populations. This resulted in short-term 10–100-fold reductions in the rabbit population, followed by its recovery with the emergence of myxomatosis-resistant animals and attenuated virus variants. The introduction of myxomatosis is regarded as a classical example of host–pathogen coevolution following cross-species transmission of a pathogen to a naive host.
Selected image
Chikungunya virus is an alphavirus transmitted by Aedes mosquitoes. The disease can cause severe joint pain, sometimes lasting for several months. Outbreaks have occurred across Africa, Asia and India, and in 2013–14, in South America and the Caribbean.
Credit: A2-33 (8 December 2013)
In the news
26 February: In the ongoing pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), more than 110 million confirmed cases, including 2.5 million deaths, have been documented globally since the outbreak began in December 2019. WHO
18 February: Seven asymptomatic cases of avian influenza A subtype H5N8, the first documented H5N8 cases in humans, are reported in Astrakhan Oblast, Russia, after more than 100,0000 hens died on a poultry farm in December. WHO
14 February: Seven cases of Ebola virus disease are reported in Gouécké, south-east Guinea. WHO
7 February: A case of Ebola virus disease is detected in North Kivu Province of the Democratic Republic of the Congo. WHO
4 February: An outbreak of Rift Valley fever is ongoing in Kenya, with 32 human cases, including 11 deaths, since the outbreak started in November. WHO
21 November: The US Food and Drug Administration (FDA) gives emergency-use authorisation to casirivimab/imdevimab, a combination monoclonal antibody (mAb) therapy for non-hospitalised people twelve years and over with mild-to-moderate COVID-19, after granting emergency-use authorisation to the single mAb bamlanivimab earlier in the month. FDA 1, 2
18 November: The outbreak of Ebola virus disease in Équateur Province, Democratic Republic of the Congo, which started in June, has been declared over; a total of 130 cases were recorded, with 55 deaths. UN
Selected article
The immune system is a system of structures and processes within an organism that protects against disease. It must detect a wide variety of pathogens – from viruses to parasitic worms – distinguish them from the organism's own healthy tissue, and neutralise them. Simple unicellular organisms such as bacteria have enzymes that protect against bacteriophage infections. Other basic immune mechanisms, including phagocytosis, antimicrobial peptides called defensins, and the complement system, evolved in ancient eukaryotes and are found in plants and invertebrates.
Humans and most other vertebrates have more sophisticated defence mechanisms, including the ability to adapt over time to recognise specific pathogens more efficiently. Adaptive immunity creates immunological memory after an initial response to a specific pathogen, leading to an enhanced response to subsequent encounters with that same pathogen. This process of acquired immunity is the basis of vaccination. Viruses and other pathogens can rapidly evolve to evade immune detection, and some viruses, notably HIV, cause the immune system to function less effectively.
Selected outbreak
The 2001 foot-and-mouth outbreak included 2,000 cases of the disease in cattle and sheep across the UK. The source was a Northumberland farm where pigs had been fed infected meat that had not been adequately sterilised. The initial cases were reported in February. The disease was concentrated in western and northern England, southern Scotland and Wales, with Cumbria being the worst-affected area. A small outbreak occurred in the Netherlands, and there were a few cases elsewhere in Europe.
The UK outbreak was controlled by the beginning of October. Control measures included stopping livestock movement and slaughtering over 6 million cows and sheep. Public access to farmland and moorland was also restricted (pictured), greatly reducing tourism in affected areas, particularly in the Lake District. Vaccination was used in the Netherlands, but not in the UK due to concerns that vaccinated livestock could not be exported. The outbreak cost an estimated £8 billion in the UK.
Selected quotation
| “ | ...the variety of genes on the planet in viruses exceeds, or is likely to exceed, that in all of the rest of life combined. | ” |
Recommended articles
Viruses & Subviral agents: bat virome • elephant endotheliotropic herpesvirus • HIV • introduction to viruses
• Playa de Oro virus • poliovirus • prion • rotavirus • virus
Diseases: colony collapse disorder • common cold • croup • dengue fever • gastroenteritis • Guillain–Barré syndrome • hepatitis B • hepatitis C • hepatitis E • herpes simplex • HIV/AIDS • influenza • meningitis • myxomatosis • polio • pneumonia • shingles • smallpox
Epidemiology & Interventions: 2007 Bernard Matthews H5N1 outbreak • Coalition for Epidemic Preparedness Innovations • Disease X • 2009 flu pandemic • HIV/AIDS in Malawi • polio vaccine • Spanish flu • West African Ebola virus epidemic
Virus–Host interactions: antibody • host • immune system • parasitism • RNA interference
Methodology: metagenomics
Social & Media: And the Band Played On • Contagion • "Flu Season" • Frank's Cock • Race Against Time: Searching for Hope in AIDS-Ravaged Africa • social history of viruses • "Steve Burdick" • "The Time Is Now" • "What Lies Below"
People: Brownie Mary • Macfarlane Burnet • Bobbi Campbell • Aniru Conteh • people with hepatitis C • HIV-positive people • Bette Korber • Henrietta Lacks • Linda Laubenstein • Barbara McClintock • poliomyelitis survivors • Joseph Sonnabend • Eli Todd • Ryan White
Selected virus
West Nile virus (WNV) is a flavivirus, an RNA virus in the Flaviviridae family. The enveloped virion is 45–50 nm in diameter and contains a single-stranded, positive-sense RNA genome of around 11,000 nucleotides, encoding ten proteins. The main natural hosts are birds (the reservoir) and several species of Culex mosquito (the vector). WNV can also infect humans and some other mammals, including horses, dogs and cats, as well as some reptiles. Transmission to humans is generally by bite of the female mosquito. Mammals form a dead end for the virus, as it cannot replicate sufficiently efficiently in them to complete the cycle back to the mosquito.
First identified in Uganda in 1937, WNV was at first mainly associated with disease in horses, with only sporadic cases of human disease until the 1990s. The virus is now endemic in Africa, west and central Asia, Oceania, the Middle East, Europe and North America. A fifth of humans infected experience West Nile fever, a flu-like disease. In less than 1% of those infected, the virus invades the central nervous system, causing encephalitis, meningitis or flaccid paralysis. No specific antiviral treatment has been licensed and only a veterinary vaccine is available. Mosquito control is the main preventive measure.
Did you know?
- ...that despite being unaffected by rabies or pseudorabies, the sea urchin Tripneustes depressus (pictured) contains antivirals to these diseases?
- ...that although Indian cassava mosaic virus does indeed infect cassava crops in India, the actual origin of the virus is unknown?
- ...that Egyptian-American physician Adel Mahmoud oversaw the development of the Gardasil HPV vaccine?
- ...that of the initial cluster of people confirmed to have been infected by a novel coronavirus in China, two-thirds had been directly exposed to the Huanan Seafood Wholesale Market in Wuhan?
- ...that Shahid Jameel and his group were the first to identify subtype C strain as the most common HIV-1 infection among Indians?
Selected biography
Françoise Barré-Sinoussi (born 30 July 1947) is a French virologist, known for being one of the researchers who discovered HIV.
Barré-Sinoussi researched retroviruses in Luc Montagnier's group at the Institut Pasteur in Paris. In 1982, she and her co-workers started to analyse samples from people with a new disease, then referred to as "gay-related immune deficiency". They found a novel retrovirus in lymph node tissue, which they called "lymphadenopathy-associated virus". Their results were published simultaneously with those of Robert Gallo's group in the USA, who had independently discovered the virus under the name "human T-lymphotropic virus type III". The virus, renamed "human immunodeficiency virus", was later shown to cause AIDS. Barré-Sinoussi continued to research HIV until her retirement in 2015, studying how the virus is transmitted from mother to child, the immune response to HIV, and how a small proportion of infected individuals, termed "long-term nonprogressors", can limit HIV replication without treatment. In 2008, she was awarded the Nobel Prize, with Montagnier, for the discovery of HIV.
In this month
February 1939: First virology journal, Archiv für die gesamte Virusforschung, appeared
8 February 1951: Establishment of the HeLa cell line from a cervical carcinoma biopsy, the first immortal human cell line
12 February 1892: Dmitri Ivanovsky (pictured) demonstrated transmission of tobacco mosaic disease by extracts filtered through Chamberland filters; sometimes considered the beginning of virology
19 February 1966: Prion disease kuru shown to be transmissible
23 February 2018: Baloxavir marboxil, the first anti-influenza agent to target the cap-dependent endonuclease activity of the viral polymerase, approved in Japan
27 February 2005: H1N1 influenza strain resistant to oseltamivir reported in a human patient
24 February 1977: Phi X 174 sequenced by Fred Sanger and coworkers, the first virus and the first DNA genome to be sequenced
28 February 1998: Publication of Andrew Wakefield's Lancet paper, subsequently discredited, linking the MMR vaccine with autism, which started the MMR vaccine controversy
Selected intervention
Several human papillomavirus (HPV) vaccines, including Cervarix and Gardasil, have been approved to protect against infections with particular types of HPV, associated with cervical and other cancers. All vaccines protect against the high-risk HPV types 16 and 18. Gardasil is a quadrivalent vaccine that additionally protects against low-risk HPV-6 and -11, which are associated with most cases of genital warts. A second-generation nine-valent Gardasil vaccine protects against five additional high-risk HPV types. It is estimated that the vaccines may prevent 70% of cervical cancer, 80% of anal cancer, 60% of vaginal cancer, 40% of vulvar cancer and possibly some oropharyngeal cancers. Protection lasts for at least 8–9 years. Some advocate giving Gardasil to men and boys with the primary aim of protecting their female sexual partners; others consider vaccinating only women and girls to be more cost effective. The licensed vaccines are subunit vaccines, containing only the L1 capsid protein of the virus, which self-assembles into virus-like particles. They are not effective in people already infected with HPV. Research is ongoing into therapeutic HPV vaccines including the viral oncoproteins, E6 and E7, but none has yet been licensed.
Subcategories
Subcategories of virology:
Topics
Things to do
- Comment on what you like and dislike about this portal
- Join the Viruses WikiProject
- Tag articles on viruses and virology with the project banner by adding {{WikiProject Viruses}} to the talk page
- Assess unassessed articles against the project standards
- Create requested pages: red-linked viruses | red-linked virus genera
- Expand a virus stub into a full article, adding images, citations, references and taxoboxes, following the project guidelines
- Create a new article (or expand an old one 5-fold) and nominate it for the main page Did You Know? section
- Improve a B-class article and nominate it for Good Article
or Featured Article
status - Suggest articles, pictures, interesting facts, events and news to be featured here on the portal
WikiProjects & Portals
WikiProject Viruses
Related WikiProjects
Medicine • Microbiology • Molecular & Cellular Biology • Veterinary Medicine
Related Portals
Associated Wikimedia
The following Wikimedia Foundation sister projects provide more on this subject:
-
Commons
Free media repository -
Wikibooks
Free textbooks and manuals -
Wikidata
Free knowledge base -
Wikinews
Free-content news -
Wikiquote
Collection of quotations -
Wikisource
Free-content library -
Wikispecies
Directory of species -
Wikiversity
Free learning tools -
Wiktionary
Dictionary and thesaurus
