Portal:Viruses

Gastroenteritis is an inflammation of the gastrointestinal tract involving both the stomach and small intestine, which results in diarrhoea and vomiting, and sometimes abdominal pain. It is usually caused by a virus: most commonly rotavirus and norovirus, but also adenovirus and astrovirus. Other major infectious causes include Campylobacter, Escherichia coli, Vibrio cholerae and some other bacteria, as well as protozoa. Viruses, particularly rotavirus, cause about 70% of gastroenteritis episodes in children, while norovirus is the leading cause of gastroenteritis among adults in America, causing over 90% of outbreaks.

Transmission can be from consumption of improperly prepared foods or contaminated water, or by close contact with infectious individuals. Good sanitation practices and a convenient supply of uncontaminated water are important for reducing infection. Personal measures such as hand washing with soap can decrease incidence by as much as 30%. An estimated 2 billion cases of gastroenteritis occurred globally in 2015, mainly among children and people in developing countries, resulting in 1.3 million deaths. Gastroenteritis is usually an acute and self-limiting disease that does not require medication; the main treatment is rehydration using oral rehydration therapy. A rotavirus vaccine is available.

Muhammad ibn Zakariya al-Razi was a Persian physician and chemist who, in the 9th century, was the first to document the distinction between the diseases of measles and smallpox.

Credit: Gerard of Cremona (c. 1250–60)

Map showing the prevalence of SARS-CoV-2 cases; black: highest prevalence; dark red to pink: decreasing prevalence; grey: no recorded cases or no data

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

Interferons are a group of signalling proteins released by host cells in response to viruses and other pathogens. They belong to a large class of proteins known as cytokines: molecules used for communication between cells to trigger the protective defences of the immune system that help to eradicate pathogens. More than twenty distinct interferon genes and proteins have been identified in animals, including humans.

When a cell is infected by a virus, several virus products, including glycoproteins and viral RNA, stimulate the cell to produce and release interferons. This causes nearby cells to heighten their defences against viral infection, and so interferes with viral replication. Some viruses, including Japanese encephalitis virus, dengue type 2 virus, human cytomegalovirus and Kaposi's sarcoma-associated herpesvirus, have evolved ways to resist interferon's antiviral activity. Interferons also have various other functions in regulating the immune system. Interferons and other cytokines are responsible for some symptoms of infection, such as fever, muscle pain and "flu-like symptoms".

In the severe acute respiratory syndrome (SARS) outbreak, the first cases of the newly emerged SARS coronavirus were reported in November 2002 from the Chinese Guangdong province. The virus soon spread across Asia, with China, Hong Kong, Taiwan and Singapore being the worst affected countries; a secondary outbreak occurred in Canada. The rapid initial spread of the outbreak has been in part attributed to China's slow response to the early cases. Over 8,000 people were infected, with a case fatality rate of 11%. Those over 65 years had a much higher mortality rate, greater than 55%. The outbreak was contained by July 2003, and no cases have been reported since 2004.

At the time of the outbreak, the immediate source of SARS coronavirus was thought to have been the masked palm civet (Paguma larvata; pictured), which was sold as food in Guangdong markets. The virus was also found in raccoon dogs, ferret badgers and domestic cats. More recent research has suggested that the natural reservoir could be horseshoe bats.

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