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| {{Flu}}
| | #REDIRECT [[Influenza virus]] |
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| __NOTOC__
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| '''H3N2''' is a subtype of the [[Influenzavirus A| influenza A virus]]. Its name derives from the forms of the two kinds of [[protein]]s on the surface of its coat, [[hemagglutinin]] (H) and [[neuraminidase]] (N). H3N2 [[virus]]es infect [[human]]s and pigs, though in each species the virus has [[mutation|mutated]] into many strains. H3N2 exchanges genes for internal proteins with other influenza subtypes.
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| The annual flu (also called "[[flu season|seasonal flu]]" or "[[human flu]]") kills an estimated 36,000 people in the United States each year. Flu [[vaccines]] are based on predicting which mutants of [[H1N1]], H3N2, [[H1N2]], and [[influenzavirus B|influenza B]] will proliferate in the next season. Separate vaccines are developed for the northern and southern hemispheres in preparation for their annual epidemics. In the tropics, influenza shows no clear seasonality.
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| In the past ten years, H3N2 has tended to dominate in prevalence over H1N1, H1N2, and influenza B. Measured resistance to the standard antiviral drugs [[amantadine]] and [[rimantadine]] in H3N2 has increased from 1% in 1994 to 12% in 2003 to 91% in 2005. <ref>[http://www.reason.com/rb/rb101905.shtml Reason] [http://www.nytimes.com/2006/01/15/health/15drugs.html New York Times]</ref>
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| ==Hong Kong Flu==<!-- This section is linked from [[Influenza]] -->
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| The Hong Kong Flu was a [[Pandemic Severity Index|category 2]] [[flu pandemic]] caused by a strain of H3N2 descended from [[H2N2]] by [[antigenic shift]], in which genes from multiple subtypes reassorted to form a new virus. The '''Hong Kong Flu''' pandemic of 1968 and 1969 infected an estimate 500,000 with a low death rate<ref name="Starling">Starling, Arthur. [2006] (2006) Plague, SARS, and the Story of Medicine in Hong Kong. HK University Press. ISBN 9622098053</ref><ref>(Detailed chart of its evolution [http://www.eletrica.ufsj.edu.br/~nepomuceno/references/epidemiology/ear_eal02.pdf here].)</ref>. In the US, 50 million were infected with an estimated 33,000 deaths<ref>Digitized Editorial Research Reports By Congressional Quarterly, inc 1986</ref>.
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| Both the [[H2N2]] and H3N2 [[pandemic flu]] strains contained [[gene]]s from [[avian influenza]] viruses. The new subtypes arose in pigs coinfected with avian and human viruses and were soon transferred to humans. Swine were considered the original "intermediate host" for influenza, because they supported reassortment of divergent subtypes. However, other hosts appear capable of similar coinfection (e.g., many poultry species), and direct transmission of avian viruses to humans is possible. H1N1 may have been transmitted directly from birds to [[human]]s (Belshe 2005). <ref>[http://www.influenzareport.com/ir/ai.htm Chapter Two : Avian Influenza by Timm C. Harder and Ortrud Werner] from excellent free on-line Book called ''Influenza Report 2006'' which is a medical textbook that provides a comprehensive overview of epidemic and pandemic influenza.''</ref>
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| The Hong Kong flu strain shared internal genes and the [[neuraminidase]] with the 1957 [[Asian Flu]] ([[H2N2]]). Accumulated antibodies to the neuraminidase or internal proteins may have resulted in much fewer casualties than most [[pandemic]]s. However, cross-immunity within and between subtypes of influenza is poorly understood.
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| The Hong Kong flu was the first known outbreak of the H3N2 strain, though there is serologic evidence of H3N? infections in the late 19th century. The first record of the outbreak in Hong Kong appeared on July 13, 1968 in an area with a density of about 500 people per acre in an urban setting. The outbreak reached maximum intensity in 2 weeks, lasting 6 weeks in total. The virus was isolated in [[Queen Mary Hospital, Hong Kong|Queen Mary Hospital]]. Flu symptoms lasted 4 to 5 days<ref name="Starling" />.
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| By July 1968, extensive outbreaks were reported in Vietnam and Singapore. By September 1968, it would reach India, Philippines, northern Australia and Europe. That same month, the virus entered US California from Vietnam War troops returning. It would reach Japan, Africa and South America by 1969<ref name="Starling" />.
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| ==See also==
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| ; strains named by isolate
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| *[[Fujian flu]]
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| ; strains named by typical host
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| *[[Avian flu|Bird flu]]
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| *Dog flu
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| *Horse flu
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| *[[Human flu]]
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| *Swine flu
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| ==Further reading==
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| *[http://www.nature.com/nature/journal/v437/n7062/fig_tab/nature04239_F1.html Graphic] showing H3N2 mutations, amino acid by amino acid, among 207 isolates completely sequenced by the [[Influenza Genome Sequencing Project]].
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| *[http://www.cdc.gov/ncidod/EID/vol11no08/05-0302.htm Influenza A (H3N2) Outbreak, Nepal]
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| *[http://www.bupa.co.uk/health_information/html/health_news/131103fujian.html Hot topic - Fujian-like strain A influenza]
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| *[http://www.idexx.com/production/swine/swine_influh3n2.jsp Monitoring Antibodies for Swine Influenza H3N2 Virus]
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| *[http://www.who.int/csr/don/2004_01_13a/en/ Human influenza A(H3N2) activity remains widespread in many countries - update 7]
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| *[http://www.who.int/csr/don/2004_01_21/en/ Human influenza A/H3N2 activity increases in many countries in central and eastern Europe - update 8]
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| *[http://www.medmall.org/Proflu/page5.html Influenza A H3N2]
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| *[http://www.newscientist.com/popuparticle.ns?id=in70 New Scientist: Bird Flu]
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| ==Sources==
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| <references/>
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| {{Influenza}}
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| [[de:Hongkong-Grippe]]
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| [[it:Influenza di Hong Kong]]
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| [[pt:Gripe de Hong Kong]]
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| [[zh:香港流感]]
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| [[Category:Influenza]]
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| [[Category:Pandemics]]
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| [[Category:Infectious disease]]
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| [[Category:Viruses]]
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