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Encyclopedia > Influenza virus
Negatively stained flu virions. These were the causative agent of the Hong Kong Flu pandemic.
Negatively stained flu virions. These were the causative agent of the Hong Kong Flu pandemic.

Influenza (or as it is commonly known, the flu or the grippe) is a contagious disease caused by an RNA virus of the orthomyxoviridae family. It rapidly spreads around the world in seasonal epidemics, imposing considerable economic burden in the form of health care costs and lost productivity. Major genetic changes in the virus have caused three influenza pandemics in the 20th century, killing many millions of people. The name comes from the old medical belief that unfavourable astrological influences cause the disease. Influenza Virus photo from http://www. ... The Hong Kong Flu was a pandemic outbreak of influenza that began in Hong Kong in 1968 and spread to the United States of America that year. ... A disease is any abnormal condition of the body or mind that causes discomfort, dysfunction, or distress to the person affected or those in contact with the person. ... An RNA virus is a virus that either uses RNA as its genetic material, or whose genetic material passes through an RNA intermediate during replication. ... Genera Influenzavirus A Influenzavirus B Influenzavirus C Isavirus Thogotovirus The Orthomyxoviridae are a family of RNA viruses which infect vertebrates. ... An epidemic is generally a widespread disease that affects many individuals in a population. ... This article is about outbreaks of disease. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... An astrological chart (or horoscope) - Y2K Chart — This particular chart is calculated for January 1, 2000 at 12:01:00 A.M. Eastern Standard Time in New York City, New York, USA. (Longitude: 074W0023 - Latitude: 40N4251), using the tropical zodiac Astrology (from Greek: αστρολογία = άστρον, astron, star + λόγος, logos, word) is...

Contents


Types

There are three types of the virus, identified by antigenic differences in their nucleoprotein and matrix protein:

  • Influenza A viruses that infect mammals and birds
  • Influenza B viruses that infect only humans
  • Influenza C viruses that infect only humans

The A type of influenza virus is the type most likely to cause epidemics and pandemics. This is because the influenza A virus can undergo antigenic shift and present a new immune target to susceptible people. Populations tend to have more resistance to influenza B and C because they only undergo antigenic drift and have more similarity with previous strains. Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals characterized by the presence of mammary glands... For other meanings of bird, see bird (disambiguation). ... An epidemic is a disease that appears as new cases in the population in a period of time at a rate (the number of new cases in the population during a specified period of time is called the incidence rate) that substantially exceeds what is expected, based on recent experence. ... This article is about outbreaks of disease. ... Antigenic shift is the process by which two different strains of influenza combine to form a new subtype which is characterized by a mixture of the surface antigens of the two original strains. ... Antigenic drift refers to mutations in the influenza virus over time. ...


Influenza A viruses can be further classified based on the viral capsid proteins hemagglutinin (HA or H) and neuraminidase (NA or N) that are essential to the virus' life cycle. Sixteen H subtypes and nine N subtypes have been identified for influenza A virus. Only one H subtype and one N subtype have been identified for influenza B virus. At present, the most common antigenic variants of influenza A virus are H1N1 and H3N2. (Yohannes et al., 2004) Hemagglutinin (HA) is an antigenic glycoprotein found on the surface of the Influenza virus and is responsible for binding the virus to the cell that is being infected. ... Neuraminidase ribbon diagram Neuraminidase is an antigenic glycoprotein enzyme (EC 3. ...


Yet further variation exists, thus specific influenza strain isolates are identified by a standard nomenclature specifying virus type, geographical location where first isolated, year of isolation, sequential number of isolation, and HA and NA subtype (Yohannes et al 2004) Examples of the nomenclature are A/Moscow/10/99 (H3N2) and B/Hong Kong/330/2001.


The term superflu is used to refer to a strain of flu that spreads unusually quickly, is unusually virulent, or is for which the host is unusually unresponsive to treatment. Thus, there is a tendency to apply the term to strains which cause epidemics or pandemics. There is no exact scientific definition of a superflu. Virulence is a term used to refer to either the relative pathogenicity or the relative ability to do damage to the host of an infectious agent. ... An epidemic is a disease that appears as new cases in the population in a period of time at a rate (the number of new cases in the population during a specified period of time is called the incidence rate) that substantially exceeds what is expected, based on recent experence. ... This article is about outbreaks of disease. ...


History

There were several serious outbreaks of influenza in the 20th century. The most famous (and the most lethal) was the Spanish Flu pandemic (type A influenza, H1N1 strain), which lasted from 1918 to 1919 and is believed to have killed more people in total than World War I.While the war casualties accumulated over several years, the pandemic took most of its toll over a period of weeks. Lesser flu pandemics included the 1957 Asian Flu (type A, H2N2 strain) and the 1968 Hong Kong Flu (type A, H3N2 strain). (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... The Spanish Flu Pandemic, also known as the Great Influenza Pandemic, the 1918 Flu Epidemic, and La Grippe, was an unusually severe and deadly strain of influenza, a viral infectious disease, that killed some 25 million to 50 million people worldwide in 1918 and 1919. ... This article is about outbreaks of disease. ... 1918 was a common year starting on Tuesday of the Gregorian calendar (see link for calendar) or a common year starting on Wednesday of the Julian calendar. ... 1919 was a common year starting on Wednesday (see link for calendar). ... World War I was primarily a European conflict with many facets: immense human sacrifice, stalemate trench warfare, and the use of new, devastating weapons - tanks, aircraft, machineguns, and poison gas. ... 1957 was a common year starting on Tuesday of the Gregorian calendar. ... The Asian Flu was a pandemic outbreak of influenza that originated in China in 1957 and spread worldwide (including to the United States of America) that same year. ... 1968 was a leap year starting on Monday (the link is to a full 1968 calendar). ... The Hong Kong Flu was a pandemic outbreak of influenza that began in Hong Kong in 1968 and spread to the United States of America that year. ...


Although there were scares in New Jersey in 1976 (the Swine Flu), worldwide in 1977 (the Russian Flu), and in Hong Kong in 1997 (Avian influenza), there have been no major pandemics subsequent to the 1968 infection. Increased immunity from antibodies and the development of flu vaccines have limited the spread of the virus and so far prevented any further pandemics. State nickname: The Garden State Other U.S. States Capital Trenton Largest city Newark Governor Richard Codey (D)Acting Official languages None defined Area 22,608 km² (47th)  - Land 19,231 km²  - Water 3,378 km² (14. ... 1976 is a leap year starting on Thursday (link will take you to calendar). ... Swine Flu is a form of influenza. ... 1977 was a common year starting on Saturday (the link is to a full 1977 calendar). ... 1997 is a common year starting on Wednesday of the Gregorian calendar. ... Influenza A virus, the virus that causes Avian flu. ... Schematic of antibody binding to an antigen An antibody is a protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... The flu vaccine is a vaccine to protect against the highly variable Influenza virus. ...


Symptoms

The virus attacks the respiratory tract, is transmitted from person to person by saliva droplets expelled by coughing, and causes the following symptoms: The respiratory system is the biological system of any organism that engages in gas exchange. ...

  • Fever
  • Headache
  • Tiredness (can be extreme)
  • Dry cough
  • Sore throat
  • Nasal congestion
  • Sneezing
  • Irritated eyes
  • Body aches
  • Extreme coldness
  • Fatigue

Influenza's effects are much more severe and last longer than those of the cold. Recovery takes about one to two weeks. Influenza can be deadly, especially for the weak, old or chronically ill. Some flu pandemics have killed millions of people. Hyperthermia: Characterized on the left. ... A headache (medically known as cephalalgia) is a condition of mild to severe pain in the head; sometimes upper back or neck pain may also be interpreted as a headache. ... Human nose Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration. ... A sneeze is the semi-autonomous, convulsive expulsion of air from the nose. ... The common cold is a mild viral infectious disease of the nose and throat; the upper respiratory system. ... This article is about outbreaks of disease. ...


Most people who get influenza will recover in one to two weeks, but others will develop life-threatening complications (such as pneumonia). Millions of people in the United States (about 10% to 20% of U.S. residents) are infected with influenza each year. An average of about 36,000 people per year in the United States die from influenza, and 114,000 per year are admitted to a hospital as a result of influenza. Even healthy people can be affected, and serious problems from influenza can happen at any age. People age 65 years and older, people of any age with chronic medical conditions, and very young children are more likely to get complications from influenza. Pneumonia, bronchitis, sinus, and ear infections are four examples of such complications. Pneumonia is an inflammation of the lung. ... Pneumonia is an inflammation of the lung. ... Bronchitis is an inflammation of the bronchi of the lungs, that causes the cilia of the bronchial epithelial cells to stop functioning. ... A sinus is a pouch or cavity in any organ or tissue, or an abnormal cavity or passage caused by the destruction of tissue. ... Otitis media (also known as glue ear) is an inflammation of the middle ear, usually associated with a buildup of fluid. ...


The flu can make chronic health problems worse. For example, people with asthma may experience asthma attacks while they have the flu, and people with chronic congestive heart failure may have worsening of this condition that is triggered by the flu. Congestive heart failure (CHF) (also called congestive cardiac failure and heart failure) is the inability of the heart to pump a sufficient amount of blood throughout the body, or requiring elevated filling pressures in order to pump effectively. ...


Variability

Influenza is an extremely variable disease; similar viruses are found in pigs and domestic fowl. In areas where there are high concentrations of humans, pigs and birds in close proximity, such as parts of Asia, simultaneous infections across species enable genetic material to be exchanged between the various strains of flu. This appears to be the principal method by which new infectious strains arise. It is believed that sooner or later, a recombination may occur to produce a strain as lethal as the 1918 virus. In late 1997, a new strain of avian influenza (also known as bird flu) called H5N1 originating from chickens infected 18 people in Hong Kong, of whom 6 died. This strain did not appear to be readily transmissible from human to human, but such a high mortality rate, and the possibility of a further recombination to make it more infectious, meant that the risk was considered so great that all domestic poultry in Hong Kong was slaughtered. Avian influenza transmissible to humans resurfaced in January 2004 in Cambodia, Vietnam, and Thailand. Influenza A virus, the virus that causes Avian flu. ... A H5N1 case in Vietnam. ...


Flu season

Influenza reaches peak prevalence in winter, and because the Northern and Southern Hemisphere have winter at different times of the year there are actually two flu seasons each year. Hope-Simpson (1981) observed that influenza outbreaks are globally ubiquitous and consistently occur six months following the time of maximum solar radiation in an area. Therefore the World Health Organization makes two vaccine formulations every year, one for the Northern and one for the Southern Hemisphere. In many parts of the world, winter is associated with snow. ... The Northern Hemisphere is the half of a planets surface (or celestial sphere) that is north of the equator (the word hemisphere literally means half ball). On Earth, the Northern Hemisphere contains most of the land and population. ... The Southern Hemisphere is the half of a planets surface (or celestial sphere) that is south of the equator (the word hemisphere literally means half ball). On Earth it contains four continents (part of Africa, Australia, most of South America, and Antarctica) and four oceans (South Atlantic, Indian, Pacific... The WHO flag: similar to the flag of the United Nations, augmented with the symbolic staff and serpent of Asklepios, Greek god of medicine and healing. ... A bottle and a syringe containing the influenza vaccine. ...


While most influenza outbreaks in the Northern Hemisphere tend to peak in January or February, not all do. For example, the influenza pandemic of 1918 and 1919 reached peak virulence during late spring and summer worldwide, and not until October in the US. It remains unclear why outbreaks of the flu occur seasonally rather than uniformly throughout the year. One possible explanation is that, because people are indoors more often during the winter, they are in close contact more often and this is enough to trigger the outbreak. Another is that the cold weakens the immune system; however, the virus is contracted in a warm indoor environment in which it can thrive. The Spanish Flu Pandemic, also known as the Great Influenza Pandemic, the 1918 Flu Epidemic, and La Grippe, was an unusually severe and deadly strain of influenza, a viral infectious disease, that killed some 25 million to 50 million people worldwide in 1918 and 1919. ...


Prevention

It is possible to get vaccinated against influenza, however, due to the high mutability of the virus a particular flu vaccine formulation usually only works for about a year. The World Health Organization co-ordinates the contents of the vaccine each year to contain the most likely strains of the virus to attack the next year. The flu vaccine is usually recommended for anyone in a high-risk group who would be likely to suffer complications from influenza. The flu vaccine is a vaccine to protect against the highly variable Influenza virus. ... The WHO flag: similar to the flag of the United Nations, augmented with the symbolic staff and serpent of Asklepios, Greek god of medicine and healing. ...


Treatment

Antiviral treatments that have proven effective in influenza are amantadine, rimantadine, zanamivir, oseltamivir and ribavirin. As most of these substances are expensive, various healthcare organisations and insurers only support their use where this would make a significant difference, e.g. in the elderly. Molecule of amantadine Amantadine, 1-adamantane amine, is an antiviral drug that was approved by the FDA in 1976 for the treatment of influenza type A in adults. ... Rimantadine is an orally administered medicine used to treat, and in rare cases prevent, type A influenza. ... Zanamivir is a neuraminidase inhibitor used in the treatment of and prophylaxis of both influenza A and influenza B. Zanamivir was the first neuraminidase inhibitor commercially developed. ... Oseltamivir is an antiviral drug, a neuraminidase inhibitor used in the treatment of and prophylaxis of both influenza A and influenza B. Oseltamivir was the first orally active neuraminidase inhibitor commercially developed. ... Ribavirin (Copegus®; Rebetol®) is an anti-viral drug active against a number of DNA and RNA viruses. ...


A trademarked elderberry extract, may aid in shortening the duration of an episode of influenza once contracted, though it has no notable preventive effects (Zakay-Rones et al 1995). Species See text Elder or Elderberry (Sambucus) is a genus of between 5-30 species of fast-growing shrubs or small trees (two species herbaceous), formerly treated in the honeysuckle family Caprifoliaceae, but now shown by genetic evidence to be correctly classified in the moschatel family Adoxaceae. ...


References

  • Hope-Simpson RE (1981). The role of season in the epidemiology of influenza. J Hyg (Lond) 86 (1), 35-47. PMID 7462597
  • Yohannes K, Roche P, Hampson A, Miller M, Spencer J (2004). Annual report of the National Influenza Surveillance Scheme, 2003. Commun Dis Intell 28 (2), 160-8. PMID 15460951
  • Zakay-Rones Z, Varsano N, Zlotnik M, Manor O, Regev L, Schlesinger M, Mumcuoglu M. Inhibition of several strains of influenza virus in vitro and reduction of symptoms by an elderberry extract (Sambucus nigra L.) during an outbreak of influenza B Panama. J Altern Complement Med. 1995 Winter;1(4):361-9. PMID 9395631.

See also

In medicine, infectious disease or communicable disease is disease caused by a biological agent (e. ... Influenza A virus, the virus that causes Avian flu. ... The Spanish Flu Pandemic, also known as the Great Influenza Pandemic, the 1918 Flu Epidemic, and La Grippe, was an unusually severe and deadly strain of influenza, a viral infectious disease, that killed some 25 million to 50 million people worldwide in 1918 and 1919. ... This article is about outbreaks of disease. ...

External links

  • Some of this article was originally from the public domain CDC publication http://www.cdc.gov/ncidod/diseases/flu/fluinfo.htm
  • WHO flu home page
  • WHO flu fact sheet
  • CDC flu page
  • BBC
  • Latest Influenza Pandemic News

  Results from FactBites:
 
Influenza Viruses, Influenza A virus, Influenza B virus, Flu Viruses, Influenza C Virus (4151 words)
Influenza is commonly seen in local outbreaks or epidemics throughout the world.
Influenza B infection is similar to influenza A, but infection with influenza C is usually subclinical or very mild in nature.
Influenza A was also associated with the cot death syndrome.
Antigenic Variation of Influenza Viruses, Influenza A Virus Antigenic Shift, Antigenic Drift (3799 words)
The appearance of a new influenza virus subtype is paralleled by the disappearance of the old subtype (an exception occurred in recent times, when 2 virus subtypes have circulated concurrently) The HA antigen is always involved in antigenic shift as it is responsible for eliciting virus-neutralizing antibodies.
Antibody to a human influenza A subtype was often found in the sera of elderly persons taken years before the appearance the appearance of the same subtype as a cause of pandemic infection.
Influenza epidemics are responsible for massive disruption to industry, and for a significant number of deaths, particularly in the elderly and the very young.
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