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| {{Influenza}} | | {| class="infobox" style="float:right;" |
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| '''For patient information click [[{{PAGENAME}} (patient information)|here]]'''
| | | [[File:Siren.gif|30px|link=Influenza resident survival guide]]|| <br> || <br> |
| | | [[Influenza resident survival guide|'''Resident'''<br>'''Survival'''<br>'''Guide''']] |
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| {{Infobox_Disease | | | {{Infobox_Disease | |
| Name = Influenza | | | Name = Influenza | |
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| Caption = [[transmission electron microscopy|TEM]] of negatively stained influenza virons, magnified approximately 70,000 times | | | Caption = [[transmission electron microscopy|TEM]] of negatively stained influenza virons, magnified approximately 70,000 times | |
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| DiseasesDB = 6791 |
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| ICD10 = {{ICD10|J|10||j|09}}, {{ICD10|J|11||j|09}} |
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| ICD9 = {{ICD9|487}} |
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| MedlinePlus = 000080 |
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| MeshID = D007251 |
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| }} | | }} |
| {{Flu}} | | __NOTOC__ |
| | {{Influenza}} |
| | '''For patient information click [[{{PAGENAME}} (patient information)|here]]''' |
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| {{CMG}}
| | '''For more information about non-human (variant) influenza viruses that may be transmitted to humans, see [[Zoonotic influenza]]''' |
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| ==[[Influenza overview|Overview]]==
| | {{CMG}}; {{AE}} {{AL}}; {{Ammu}} |
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| ==[[Influenza historical perspective|Historical perspective]]==
| | {{SK}} Flu; influenza A; influenza B; influenza C; human influenza; human influenza virus |
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| | ==[[Influenza overview|Overview]]== |
| | ==[[Influenza historical perspective|Historical Perspective]]== |
| ==[[Influenza classification|Classification]]== | | ==[[Influenza classification|Classification]]== |
| | ==[[Influenza pathophysiology |Pathophysiology]]== |
| | ==[[Influenza causes|Causes]]== |
| | ==[[Influenza differential diagnosis|Differentiating Influenza from other Diseases]]== |
| | ==[[Influenza epidemiology and demographics|Epidemiology and Demographics]]== |
| | ==[[Influenza risk factors|Risk Factors]]== |
| | ==[[Influenza natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
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| ==Diagnosis== | | ==Diagnosis== |
| | | [[Influenza history and symptoms|History and Symptoms]] | [[Influenza physical examination|Physical Examination]] | [[Influenza laboratory findings|Laboratory Findings]] | [[Influenza chest x ray|Chest X Ray]] | [[Influenza other diagnostic studies|Other Diagnostic Studies]] |
| ==[[History & Symptoms]]==
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| ===Laboratory tests===
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| The available laboratory tests for influenza continue to improve. The United States [[Centers for Disease Control and Prevention]] (CDC) maintains an up-to-date summary of available laboratory tests.<ref>Centers for Disease Control and Prevention. [http://www.cdc.gov/flu/professionals/labdiagnosis.htm Lab Diagnosis of Influenza.] Accessed on January 1, 2007</ref> According to the CDC, rapid diagnostic tests have a sensitivity of 70–75% and specificity of 90–95% when compared with viral culture. These tests may be especially useful during the influenza season (prevalence=25%) but in the absence of a local outbreak, or peri-influenza season (prevalence=10%<ref name="pimd12965940"/>).
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| ==[[Influenza epidemiology and demographics|Epidemiology & Demographics]]==
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| ==Prevention==
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| ===Vaccination and infection control===
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| {{further|[[Flu vaccine]]}}
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| [[Image:Vaccination.jpg|thumb|240px|left|U.S. Navy personnel receiving influenza vaccination]]
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| Vaccination against influenza with a [[flu vaccine]] is strongly recommended for high-risk groups, such as children and the elderly.
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| Flu vaccines can be produced in several ways; the most common method is to grow the virus in fertilised hen eggs. After purification, the virus is inactivated (for example, by treatment with detergent) to produce an inactivated-virus vaccine. Alternatively, the virus can be grown in eggs until it loses [[virulence]] and the avirulent virus given as a live vaccine.<ref name=Hilleman/> The effectiveness of these flu vaccines is variable. Due to the high mutation rate of the virus, a particular flu vaccine usually confers protection for no more than a few years. Every year, the [[World Health Organization]] predicts which strains of the virus are most likely to be circulating in the next year, allowing [[pharmaceutical company|pharmaceutical companies]] to develop vaccines that will provide the best immunity against these strains.<ref name= WHOrecommendation/> Vaccines have also been developed to protect poultry from [[avian influenza]]. These vaccines can be effective against multiple strains and are used either as part of a preventative strategy, or combined with culling in attempts to eradicate outbreaks.<ref>{{cite journal | last = Capua | first = I | coauthors = Alexander D | title = The challenge of avian influenza to the veterinary community. | url= http://taylorandfrancis.metapress.com/media/gmuaahtvwk6vweuhugdh/contributions/t/2/n/2/t2n2431j4u176p7g.pdf | journal = Avian Pathol | volume = 35 | issue = 3 | pages = 189–205 | year = 2006 | id = PMID 16753610}}</ref>
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| It is possible to get vaccinated and still get influenza. The vaccine is reformulated each season for a few specific flu strains, but cannot possibly include all the strains actively infecting people in the world for that season. It takes about six months for the manufacturers to formulate and produce the millions of doses required to deal with the seasonal epidemics; occasionally, a new or overlooked strain becomes prominent during that time and infects people although they have been vaccinated (as by the [[Fujian flu|H3N2 Fujian flu]] in the 2003–2004 flu season).<ref>{{cite journal | last = Holmes | first = E | coauthors = Ghedin E, Miller N, Taylor J, Bao Y, St George K, Grenfell B, Salzberg S, Fraser C, Lipman D, Taubenberger J | title = Whole-genome analysis of human influenza A virus reveals multiple persistent lineages and reassortment among recent H3N2 viruses | journal = PLoS Biol | volume = 3 | issue = 9 | pages = e300 | year = 2005 | id = PMID 16026181}}</ref> It is also possible to get infected just before vaccination and get sick with the very strain that the vaccine is supposed to prevent, as the vaccine takes about two weeks to become effective.<ref name=CDCkeyfacts/>
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| The 2006–2007 season is the first in which the CDC has recommended that children younger than 59 months receive the annual flu vaccine.<ref name=cdcreport> [http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5510a1.htm Prevention and Control of Influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP)] CDC report (MMWR 2006 Jul 28;55(RR10):1–42) accessed 19 Oct 2006.</ref> Vaccines can cause the [[immune system]] to react as if the body were actually being infected, and general infection symptoms (many cold and flu symptoms are just general infection symptoms) can appear, though these symptoms are usually not as severe or long-lasting as influenza. The most dangerous side-effect is a severe [[allergy|allergic reaction]] to either the virus material itself, or residues from the hen eggs used to grow the influenza; however, these reactions are extremely rare.<ref>[http://www.cdc.gov/flu/about/qa/flushot.htm Questions & Answers: Flu Shot] CDC publication updated Jul 24, 2006. Accessed 19 Oct 06.</ref>
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| [[Influenza pandemic#Personal health and hygiene|Good personal health and hygiene habits]] are reasonably effective in avoiding and minimizing influenza. People who contract influenza are most infective between the second and third days after infection and infectivity lasts for around 10 days.<ref name=Carrat>{{cite journal |author=Carrat F, Luong J, Lao H, Sallé A, Lajaunie C, Wackernagel H |title=A 'small-world-like' model for comparing interventions aimed at preventing and controlling influenza pandemics |url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=17059593 |journal=BMC Med |volume=4 |issue= |pages=26 |year= |pmid=17059593}}</ref> Children are notably more infectious than adults, and shed virus from just before they develop symptoms until 2 weeks after infection.<ref name=Carrat/><ref>{{cite journal |author=Mitamura K, Sugaya N |title=[Diagnosis and Treatment of influenza—clinical investigation on viral shedding in children with influenza] |journal=Uirusu |volume=56 |issue=1 |pages=109-16 |year=2006 |pmid=17038819}}</ref> | |
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| Since influenza spreads through [[particulate|aerosols]] and contact with contaminated surfaces, it is important to persuade people to cover their mouths while sneezing and to wash their hands regularly.<ref name=cdcreport/> Surface sanitizing is recommended in areas where influenza may be present on surfaces.<ref>{{cite journal |author=Hota B |title=Contamination, disinfection, and cross-colonization: are hospital surfaces reservoirs for nosocomial infection? |journal=Clin Infect Dis |volume=39 |issue=8 |pages=1182–9 |year=2004 |id=PMID 15486843}}</ref> [[Alcohol]] is an effective sanitizer against influenza viruses, while [[quaternary ammonium]] compounds can be used with alcohol, to increase the duration of the sanitizing action.<ref name=McDonnell>{{cite journal |author=McDonnell G, Russell A |title=Antiseptics and disinfectants: activity, action, and resistance |url=http://cmr.asm.org/cgi/content/full/12/1/147?view=long&pmid=9880479 |journal=Clin Microbiol Rev |volume=12 |issue=1 |pages=147-79 |year=1999 |id=PMID 9880479}}</ref> In hospitals, [[quaternary ammonium]] compounds and halogen-releasing agents such as [[sodium hypochlorite]] are commonly used to sanitize rooms or equipment that have been occupied by patients with influenza symptoms.<ref name=McDonnell/> During past pandemics, closing schools, churches and theaters slowed the spread of the virus but did not have a large effect on the overall death rate.<ref>{{cite journal |author=Hatchett RJ, Mecher CE, Lipsitch M |title=Public health interventions and epidemic intensity during the 1918 influenza pandemic |url=http://www.pnas.org/cgi/content/full/104/18/7582 |journal=Proc Natl Acad Sci U S A. |volume=104 |issue=18 |pages=7582–7587 |year=2007 |pmid=17416679}}</ref><ref>{{cite journal |author=Bootsma MC, Ferguson NM |title=The effect of public health measures on the 1918 influenza pandemic in U.S. cities |url=http://www.pnas.org/cgi/content/full/104/18/7588 |journal=Proc Natl Acad Sci U S A. |volume=104 |issue=18 |pages=7588–7593 |year=2007 |pmid=17416677}}</ref>
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| ==Treatment== | | ==Treatment== |
| {{further|[[Influenza treatment]]}}
| | [[Influenza medical therapy|Medical Therapy]] | [[Influenza primary prevention|Primary Prevention]] | [[Influenza cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Influenza future or investigational therapies|Future or Investigational Therapies]] |
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| People with the flu are advised to get plenty of rest, drink a lot of liquids, avoid using [[alcoholic beverage|alcohol]] and [[tobacco smoking|tobacco]] and, if necessary, take medications such as [[paracetamol]] (acetaminophen) to relieve the fever and muscle aches associated with the flu. Children and teenagers with flu symptoms (particularly fever) should avoid taking [[aspirin]] during an influenza infection (especially [[Influenzavirus B|influenza type B]]) because doing so can lead to [[Reye's syndrome]], a rare but potentially fatal disease of the [[liver]].<ref>{{cite journal | last = Glasgow | first = J | coauthors = Middleton B | title = Reye syndrome — insights on causation and prognosis | url=http://adc.bmjjournals.com/cgi/content/full/85/5/351 | journal = Arch Dis Child | volume = 85 | issue = 5 | pages = 351–3 | year = 2001 | id = PMID 11668090}}</ref> Since influenza is caused by a virus, [[antibiotic]]s have no effect on the infection; unless prescribed for [[secondary infection]]s such as [[bacterial pneumonia]], they may lead to resistant bacteria. Antiviral medication is sometimes effective, but viruses can develop resistance to the standard antiviral drugs.
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| The two classes of anti-virals are neuraminidase inhibitors and M2 inhibitors ([[adamantane]] derivatives). Neuraminidase inhibitors are currently preferred for flu virus infections. The CDC recommended against using M2 inhibitors during the 2005–06 influenza season.<ref>Centers for Disease Control and Prevention. [http://www.cdc.gov/flu/han011406.htm CDC Recommends against the Use of Amantadine and Rimantadine for the Treatment or Prophylaxis of Influenza in the United States during the 2005–06 Influenza Season.] [[January 14]], [[2006]]. Retrieved on [[2007-01-01]]</ref>
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| ===Neuraminidase inhibitors===
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| Antiviral drugs such as [[oseltamivir]] (trade name Tamiflu) and [[zanamivir]] (trade name Relenza) are [[neuraminidase inhibitor]]s that are designed to halt the spread of the virus in the body.<ref name= Neuraminidase_inhibitors>{{cite journal | last = Moscona | first = A | title = Neuraminidase inhibitors for influenza | url=http://content.nejm.org/cgi/content/full/353/13/1363 | journal = N Engl J Med | volume = 353 | issue = 13 | pages = 1363–73 | year = 2005 | id = PMID 16192481}}</ref> These drugs are often effective against both influenza A and B.<ref name=Stephenson/> The [[Cochrane Collaboration]] reviewed these drugs and concluded that they reduce symptoms and complications.<ref name="pmid16855962">{{cite journal | last = Jefferson | first = T | coauthors = Demicheli V, Di Pietrantonj C, Jones M, Rivetti D | title = Neuraminidase inhibitors for preventing and treating influenza in healthy adults | journal = Cochrane Database Syst Rev | volume = 3 | issue = | pages = CD001265 | year = | doi = 10.1002/14651858.CD001265.pub2 | id = PMID 16855962}}</ref> Different strains of influenza virus have differing degrees of resistance against these antivirals and it is impossible to predict what degree of resistance a future pandemic strain might have.<ref> {{cite journal | last = Webster | first = Robert G. | title = H5N1 Influenza — Continuing Evolution and Spread | url=http://content.nejm.org/cgi/content/full/355/21/2174 | journal = N Engl J Med | volume = 355 | issue = 21 | pages = 2174–77 | year = 2006 | id = PMID 16192481}}</ref>
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| ===M2 inhibitors (adamantanes) ===
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| The [[antiviral drug]]s [[amantadine]] and [[rimantadine]] are designed to block a viral [[ion channel]] and prevent the virus from infecting cells. These drugs are sometimes effective against influenza A if given early in the infection, but are always ineffective against influenza B.<ref name= Stephenson>{{cite journal | last = Stephenson | first = I | coauthors = Nicholson K | title = Chemotherapeutic control of influenza | url=http://jac.oxfordjournals.org/cgi/content/full/44/1/6 | journal = J Antimicrob Chemother | volume = 44 | issue = 1 | pages = 6–10 | year = 1999 | id = PMID 10459804}}</ref> Measured resistance to amantadine and rimantadine in American isolates of [[H3N2]] has increased to 91% in 2005.<ref>{{cite journal | author = | title = High levels of adamantane resistance among influenza A (H3N2) viruses and interim guidelines for use of antiviral agents — United States, 2005–06 influenza season | url=http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5502a7.htm | journal = MMWR Morb Mortal Wkly Rep | volume = 55 | issue = 2 | pages = 44–6 | year = 2006 | id = PMID 16424859}}</ref>
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| ==Research==
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| {{further|[[Influenza research]]}}
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| [[Image:Influenza research.jpg|thumb|220px|right|CDC scientist working on influenza under high bio-safety conditions]]
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| Research on influenza includes studies on [[molecular virology]], how the virus produces disease ([[pathogenesis]]), host [[immune response]]s, [[genomics|viral genomics]], and how the virus spreads ([[epidemiology]]). These studies help in developing influenza countermeasures; for example, a better understanding of the body's immune response helps [[vaccine]] development, and a detailed picture of how influenza invades cells aids the development of antiviral drugs. One important basic research program is the [[Influenza Genome Sequencing Project]], which is creating a library of influenza sequences; this library should help clarify which factors make one strain more lethal than another, which genes most affect [[immunogenicity]], and how the virus [[evolution|evolves]] over time.<ref> [http://msc.tigr.org/infl_a_virus/index.shtml Influenza A Virus Genome Project] at The Institute of Genomic Research. Accessed 19 Oct 06</ref>
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| Research into new vaccines is particularly important: as current vaccines are slow and expensive to produce and must be reformulated every year. The sequencing of the influenza genome and [[recombinant DNA]] technology may accelerate the generation of new vaccine strains by allowing scientists to substitute new antigens into a previously-developed vaccine strain.<ref>{{cite journal | author = Subbarao K, Katz J | title = Influenza vaccines generated by reverse genetics. | journal = Curr Top Microbiol Immunol | volume = 283 | issue = | pages = 313-42 | year = | id = PMID 15298174}}</ref> New technologies are also being developed to grow virus in [[cell culture]]; which promises higher yields, less cost, better quality and surge capacity.<ref>{{cite journal | author = Bardiya N, Bae J | title = Influenza vaccines: recent advances in production technologies. | url=http://www.springerlink.com/content/jdt26gc39v4bwk9q/ | journal = Appl Microbiol Biotechnol | volume = 67 | issue = 3 | pages = 299–305 | year = 2005 | id = PMID 15660212}}</ref> The U.S. government has purchased from [[Sanofi Pasteur]] and [[Chiron Corporation]] several million doses of vaccine meant to be used in case of an [[influenza pandemic]] of [[H5N1]] avian influenza and is conducting clinical trials with these vaccines.<ref> [http://www.nytimes.com/2006/03/30/health/30vaccine.html?_r=1&oref=slogin New York Times article ""Doubt Cast on Stockpile of a Vaccine for Bird Flu""] by Denise Grady. Published: March 30, 2006. Accessed 19 Oct 06</ref> The UK government is also stockpiling millions of antiviral drugs(tamiflu, oseltamivir, zanimivir) to give to its citizens in the event of an outbreak, the UK [[Health Protection Agency]] has also gathered a limited amount of HPAI H5N1 vaccines for experimental purposes.
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| ==Infection in other animals==
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| {{H5N1}}{{further|[[Influenzavirus A]], [[H5N1]] and [[Transmission and infection of H5N1]]}}
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| Influenza infects many animal species and transfer of viral strains between species can occur. Birds are thought to be the main [[host (biology)|animal reservoir]]s of influenza viruses.<ref>{{cite journal | author = Gorman O, Bean W, Kawaoka Y, Webster R | title = Evolution of the nucleoprotein gene of influenza A virus. | url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=2319644 | journal = J Virol | volume = 64 | issue = 4 | pages = 1487–97 | year = 1990 | id = PMID 2319644}}</ref> Sixteen forms of [[hemagglutinin]] and 9 forms of [[neuraminidase]] have been identified. All known subtypes (HxNy) are found in birds but many subtypes are endemic in humans, dogs, horses, and pigs; populations of camels, ferrets, cats, seals, mink, and whales also show evidence of prior infection or exposure to influenza.<ref name=webster/> Variants of flu virus are sometimes named according to the species the strain is endemic in or adapted to. The main variants named using this convention are: Bird flu, [[Human flu|Human Flu]], Swine Flu, Horse Flu and Dog Flu. (Cat flu generally refers to Feline viral rhinotracheitis or Feline calicivirus and not infection from an influenza virus.) In pigs, horses and dogs, influenza symptoms are similar to humans, with cough, fever and loss of appetite.<ref name=webster/> The frequency of animal diseases are not as well-studied as human infection, but an outbreak of influenza in harbour seals caused approximately 500 seal deaths off the New England coast in 1979–1980.<ref>{{cite journal | author = Hinshaw V, Bean W, Webster R, Rehg J, Fiorelli P, Early G, Geraci J, St Aubin D | title = Are seals frequently infected with avian influenza viruses? | url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=6471169 | journal = J Virol | volume = 51 | issue = 3 | pages = 863-5 | year = 1984 | id = PMID 6471169}}</ref> On the other hand, outbreaks in pigs are common and do not cause severe mortality.<ref name=webster/> | |
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| Flu symptoms in birds are variable and can be unspecific.<ref>{{cite journal | author = Elbers A, Koch G, Bouma A | title = Performance of clinical signs in poultry for the detection of outbreaks during the avian influenza A (H7N7) epidemic in The Netherlands in 2003. | journal = Avian Pathol | volume = 34 | issue = 3 | pages = 181-7 | year = 2005 | id = PMID 16191700}}</ref> The symptoms following infection with low-pathogenicity avian influenza may be as mild as ruffled feathers, a small reduction in egg production, or weight loss combined with minor respiratory disease.<ref>Capua I, Mutinelli F. "Low pathogenicity (LPAI) and highly pathogenic (HPAI) avian influenza in turkeys and chicken." In: Capua I, Mutinelli F. (eds.), A Colour Atlas and Text on Avian Influenza, Papi Editore, Bologna, 2001, pp. 13–20</ref> Since these mild symptoms can make diagnosis in the field difficult, tracking the spread of avian influenza requires laboratory testing of samples from infected birds. Some strains such as Asian [[H9N2]] are highly virulent to poultry, and may cause more extreme symptoms and significant mortality.<ref>{{cite journal | author = Bano S, Naeem K, Malik S | title = Evaluation of pathogenic potential of avian influenza virus serotype H9N2 in chickens. | journal = Avian Dis | volume = 47 | issue = 3 Suppl | pages = 817-22 | year = 2003 | id = PMID 14575070}}</ref> In its most highly pathogenic form, influenza in chickens and turkeys produces a sudden appearance of severe symptoms and almost 100% mortality within two days.<ref>{{cite journal | author = Swayne D, Suarez D | title = Highly pathogenic avian influenza. | journal = Rev Sci Tech | volume = 19 | issue = 2 | pages = 463-82 | year = 2000 | id = PMID 10935274}}</ref> As the virus spreads rapidly in the crowded conditions seen in the intensive farming of chickens and turkeys, these outbreaks can cause large economic losses to poultry farmers.
| | ==Case Studies== |
| | :[[Influenza case study one|Case #1]] |
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| An avian-adapted, highly pathogenic strain of H5N1 (called HPAI A(H5N1), for "highly pathogenic avian influenza virus of type A of subtype H5N1") causes [[transmission and infection of H5N1|H5N1 flu]], commonly known as "avian influenza" or simply "bird flu", and is [[endemic (epidemiology)|endemic]] in many bird populations, especially in Southeast Asia. This Asian lineage strain of HPAI A(H5N1) is [[global spread of H5N1|spreading globally]]. It is [[epizootic]] (an epidemic in non-humans) and panzootic (a disease affecting animals of many species, especially over a wide area) killing tens of millions of birds and spurring the culling of hundreds of millions of other birds in an attempt to control its spread. Most references in the media to "bird flu" and most references to H5N1 are about this specific strain.<ref>{{cite journal | author = Li K, Guan Y, Wang J, Smith G, Xu K, Duan L, Rahardjo A, Puthavathana P, Buranathai C, Nguyen T, Estoepangestie A, Chaisingh A, Auewarakul P, Long H, Hanh N, Webby R, Poon L, Chen H, Shortridge K, Yuen K, Webster R, Peiris J | title = Genesis of a highly pathogenic and potentially pandemic H5N1 influenza virus in eastern Asia. | journal = Nature | volume = 430 | issue = 6996 | pages = 209-13 | year = 2004 | id = PMID 15241415}}</ref><ref>Li KS, Guan Y, Wang J, Smith GJ, Xu KM, Duan L, Rahardjo AP, Puthavathana P, Buranathai C, Nguyen TD, Estoepangestie AT, Chaisingh A, Auewarakul P, Long HT, Hanh NT, Webby RJ, Poon LL, Chen H, Shortridge KF, Yuen KY, Webster RG, Peiris JS. [http://darwin.nap.edu/books/0309095042/html/116.html "The Threat of Pandemic Influenza: Are We Ready?" Workshop Summary] The National Academies Press (2005) "Today's Pandemic Threat: Genesis of a Highly Pathogenic and Potentially Pandemic H5N1 Influenza Virus in Eastern Asia", pages 116–130</ref>
| | ==Related Chapters== |
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| At present, HPAI A(H5N1) is an avian disease and there is no evidence suggesting efficient human-to-human transmission of HPAI A(H5N1). In almost all cases, those infected have had extensive physical contact with infected birds.<ref>{{cite journal | author = Liu J | title = Avian influenza—a pandemic waiting to happen? | url=http://jmii.org/content/pdf/v39n1p4.pdf | journal = J Microbiol Immunol Infect | volume = 39 | issue = 1 | pages = 4–10 | year = 2006 | id = PMID 16440117}}</ref> In the future, H5N1 may mutate or reassort into a strain capable of efficient human-to-human transmission. Due to its high lethality and [[virulence]], its [[endemic (epidemiology)|endemic]] presence, and its large and increasing biological host reservoir, the H5N1 virus is the world's pandemic threat in the 2006–7 flu season, and billions of dollars are being raised and spent researching H5N1 and preparing for a potential [[influenza pandemic]].<ref name=Rosenthal> Rosenthal, E. and Bradsher, K. [http://www.nytimes.com/2006/03/16/business/16bird.html?_r=1&oref=slogin Is Business Ready for a Flu Pandemic?] The New York Times 16-03-2006 Accessed 17-04-2006</ref>
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| ==Economic impact==
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| {{further|[[Social impact of H5N1]]}}
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| Influenza produces [[variable cost|direct cost]]s due to lost [[productivity]] and associated medical treatment, as well as [[indirect costs]] of preventative measures. In the United States, influenza is responsible for a total cost of over $10 billion per year, while it has been estimated that a future pandemic could cause hundreds of billions of dollars in direct and indirect costs.<ref>[http://www.whitehouse.gov/homeland/pandemic-influenza.html Statement from President George W. Bush on Influenza] Accessed 26 Oct 2006</ref> However, the economic impact of past pandemics have not been intensively studied, and some authors have suggested that the [[Spanish flu|Spanish influenza]] actually had a positive long-term effect on per-capita income growth, despite a large reduction in the working population and severe short-term depressive effects.<ref>Brainerd, E. and M. Siegler (2003), “The Economic Effects of the 1918 Influenza Epidemic”, ''CEPR Discussion Paper'', no. 3791.</ref> Other studies have attempted to predict the costs of a pandemic as serious as the 1918 Spanish flu on the U.S. economy, where 30% of all workers became ill, and 2.5% were killed. A 30% sickness rate and a three-week length of illness would decrease [[gross domestic product]] by 5%. Additional costs would come from medical treatment of 18 million to 45 million people, and total economic costs would be approximately $700 billion.<ref>{{cite journal | author = Poland G | title = Vaccines against avian influenza—a race against time. | url=http://content.nejm.org/cgi/content/full/354/13/1411 | journal = N Engl J Med | volume = 354 | issue = 13 | pages = 1411–3 | year = 2006 | id = PMID 16571885}}</ref>
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| Preventative costs are also high. Governments worldwide have spent billions of U.S. dollars preparing and planning for a potential H5N1 avian influenza pandemic, with costs associated with purchasing drugs and vaccines as well as developing disaster drills and strategies for improved border controls.<ref name=Rosenthal/> On November 1 2005, President George W. Bush unveiled the National Strategy to Safeguard Against the Danger of Pandemic Influenza<ref>[http://www.whitehouse.gov/homeland/pandemic-influenza.html National Strategy for Pandemic Influenza] Whitehouse.gov Accessed 26 Oct 2006.</ref> backed by a request to Congress for $7.1 billion to begin implementing the plan.<ref>[http://usinfo.state.gov/gi/Archive/2005/Nov/01-432345.html Bush Outlines $7 Billion Pandemic Flu Preparedness Plan] State.gov. Accessed 26 Oct 2006</ref> Internationally, on January 18 2006 donor nations pledged US$2 billion to combat bird flu at the two-day International Pledging Conference on Avian and Human Influenza held in China.<ref>[http://www.ens-newswire.com/ens/jan2006/2006-01-18-02.asp Donor Nations Pledge $1.85 Billion to Combat Bird Flu] Newswire Accessed 26 Oct 2006.</ref>
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| Up to 2006, over ten billion dollars have been spent and over two hundred million birds have been killed to try to contain H5N1 avian influenza.<ref>[http://www.usaid.gov/about_usaid/acvfa/intro_ai.pdf Avian Influenza and its Global Implications] US AID. Accessed 26 Oct 2006.</ref> However, as these efforts have been largely ineffective at controlling the spread of the virus, other approaches are being tried: for example, the Vietnamese government in 2005 adopted a combination of mass poultry vaccination, disinfecting, culling, information campaigns and bans on live poultry in cities.<ref> [http://today.reuters.co.uk/news/newsArticle.aspx?type=worldNews&storyID=2006-04-28T080147Z_01_HAN5054_RTRUKOC_0_UK-BIRDFLU-VIETNAM.xml Reuters Vietnam to unveil advanced plan to fight bird flu] published on April 28, 2006. Accessed 26 Oct 2006</ref> As a result of such measures, the cost of poultry farming has increased, while the cost to consumers has gone down due to demand for poultry falling below supply. This has resulted in devastating losses for many farmers. Poor poultry farmers cannot afford mandated measures which keep their bird livestock from contact with wild birds (and other measures), thus risking losing their livelihood altogether. Multinational poultry farming is increasingly becoming unprofitable as H5N1 avian influenza becomes endemic in wild birds worldwide.<ref>[http://www.irinnews.org/report.asp?ReportID=52471 Poultry sector suffers despite absence of bird flu] UN Office for the Coordination of Humanitarian Affairs. Accessed 26 Oct 2006</ref> Financial ruin for poor poultry farmers, which can be as severe as threatening starvation, has caused some to commit [[suicide]] and many others to stop cooperating with efforts to deal with this virus – further increasing the human toll, the spread of the disease, and the chances of a pandemic mutation.<ref>[http://www.expressindia.com/fullstory.php?newsid=65957 Nine poultry farmers commit suicide in flu-hit India] Reuters. Published on April 12, 2006. Accessed 26 Oct 2006.</ref><ref>[http://www.nytimes.com/2006/04/14/world/africa/14egypt.html?_r=1&oref=slogin In the Nile Delta, Bird Flu Preys on Ignorance and Poverty] The New York Times. Published on April 13, 2006. Accessed 26 Oct 2006.</ref>
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| ==See also==
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| <!-- Please do not add links already featured in the body of the article above --> | | <!-- Please do not add links already featured in the body of the article above --> |
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| *[[Center for Biologics Evaluation and Research]] | | *[[Center for Biologics Evaluation and Research]] |
| *[[H5N1 genetic structure]] | | *[[H5N1 genetic structure]] |
| | *[[ICEID]] |
| | *[[Influenza Genome Sequencing Project]] |
| | *[[Cytokine storm]] |
| | *[[International Partnership on Avian and Pandemic Influenza]] |
| | *[[National Influenza Centers]] |
| | *[[Pandemic Preparedness and Response Act]] |
| | *[[Global Alliance for Vaccines and Immunization]] |
| | *[[IFPMA]] International Federation of Pharmaceutical Manufacturers Associations |
| | *[[Reporting disease cases]] |
| | *[[Original antigenic sin]] |
| | *[[Center for Biologics Evaluation and Research]] |
| *[[ICEID]] | | *[[ICEID]] |
| *[[Influenza Genome Sequencing Project]] | | *[[Influenza Genome Sequencing Project]] |
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| ==References and notes== | | ==Further Readings== |
| {{reflist|2}} | | {| style=width:85%" |
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| ==Further reading==
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| *[http://www.who.int/csr/resources/publications/influenza/WHO_CDS_EPR_GIP_2006_3C.pdf WHO's assessment of Flu Research] as of November 2006. | | *[http://www.who.int/csr/resources/publications/influenza/WHO_CDS_EPR_GIP_2006_3C.pdf WHO's assessment of Flu Research] as of November 2006. |
| {{Col-end}} | | {{Col-end}} |
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| ==External links== | | ==External Links== |
| *[http://www.cdc.gov/flu/ Info on influenza] at [[Centers for Disease Control and Prevention|CDC]] | | *[http://www.cdc.gov/flu/ Info on influenza] at [[Centers for Disease Control and Prevention|CDC]] |
| *[http://www.who.int/mediacentre/factsheets/fs211/en/index.html Fact Sheet] Overview of influenza at [[World Health Organization]] | | *[http://www.who.int/mediacentre/factsheets/fs211/en/index.html Fact Sheet] Overview of influenza at [[World Health Organization]] |
| *[http://www.nhsdirect.nhs.uk/en.aspx?articleId=163§ionId=1725 Health encyclopedia entry] at [[NHS Direct]]
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| *[http://www.biohealthbase.org/ BioHealthBase Bioinformatics Resource Center] Database of influenza sequences and related information.
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| *[http://www.medicinenet.com/influenza/article.htm Overview of influenza] at [[MedicineNet]]
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| *[http://digital.library.unt.edu/govdocs/crs/search.tkl?q=influenza&search_crit=subject&search=Search&date1=Anytime&date2=Anytime&type=form Congressional Research Service (CRS) Reports regarding Influenza] Law related government reports at [[University of North Texas]]
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| *[http://www.fluwikie.com/index.php?n=Geographic.Geographic Influenza Surveillance and Contingency Plans] (by Country/Region)
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| *[http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/46000000.htm Orthomyxoviridae] The Universal Virus Database of the [[International Committee on Taxonomy of Viruses]] | | *[http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/46000000.htm Orthomyxoviridae] The Universal Virus Database of the [[International Committee on Taxonomy of Viruses]] |
| *[http://www.ncbi.nlm.nih.gov/genomes/FLU/flubiology.html Influenza Virus Resource] from the [[National Center for Biotechnology Information|NCBI]] | | *[http://www.ncbi.nlm.nih.gov/genomes/FLU/flubiology.html Influenza Virus Resource] from the [[National Center for Biotechnology Information|NCBI]] |
| *[http://www.influenzaworld.com/portal/eipf/pb/t/iwc/home InfluenzaWorld] Resource for all influenza-related information.
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| {{Viral diseases}} | | {{Viral diseases}} |
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| [[Category:Pulmonology]] | | [[Category:Pulmonology]] |
| [[Category:Influenza| ]] | | [[Category:Influenza| ]] |
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