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Influenzavirus C is a genus in the virus family Orthomyxoviridae, which includes those viruses which cause influenza. The species in this genus is called "Influenza C virus". Influenza C viruses are known to infect humans and pigs. Flu due to the type C species is rare compared to types A or B, but can be severe and can cause local epidemics. Subtype C has 7 RNA segments and encodes 9 proteins, while types A and B have 8 RNA segments and encode at least 10 proteins. == Influenza C virus == Influenza viruses are members of the family ''Orthomyxoviridae''.〔Pattison, McMullin, Bradbury, Alexander. Poultry Diseases 6th Edition. Elsevier Limited. 2008. P.317. ISBN 978-0-7020-28625.〕 Influenza viruses A, B and C represent the three antigenic types of influenza viruses.〔“Seasonal Influenza (Flu)” Centers for Disease Control and Prevention. March 22, 2012. http://www.cdc.gov/flu/about/viruses/types.htm〕 Of the three antigenic types, influenza virus A is the most severe, influenza virus B is less severe but can still cause outbreaks, and influenza virus C is usually only associated with minor symptoms.〔Margaret Hunt. “Microbiology and Immunology On-line” University of South Carolina School of Medicine. 2009. http://pathmicro.med.sc.edu/mhunt/flu.htm〕 Influenza virus A can infect a variety of animals as well as humans and its natural host or reservoir is birds whereas influenza viruses B and C do not have animal reservoirs.〔〔“Review of latest available evidence on potential transmission of avian influenza (H5H1) through water and sewage and ways to reduce the risks to human health” World Health Organization. 2006. http://www.who.int/water_sanitation_health/emerging/h5n1 background.pdf〕 Influenza virus C is not as easily isolated so less information is known of this type, but studies show that it occurs worldwide.〔Manuguerra JC, Hannoun C, Saenz MDC, Villarand E, Cabezas JA. 1994. “Sero-Epidemiological Survey of Influenza C Virus Infection in Spain” European Journal of Epidemiology. 10(1):91-94.〕 This virus may be spread from person to person through respiratory droplets or by fomites (non-living material) due to its ability to survive on surfaces for short durations.〔 Influenza viruses have a relatively short incubation period (lapse of time from exposure to pathogen to the appearance of symptoms) of 18–72 hours and infect the epithelial cells of the respiratory tract.〔 Influenza virus C tends to cause mild upper respiratory infections.〔Wagaman PC, Spence HA, and O’Callaghan RJ. 1989. “Detection of Influenza C Virus by Using an In Situ Esterase Assay” Journal of Clinical Microbiology. 1:832-836.〕 Cold-like symptoms are associated with the virus including fever (38-40ᵒC), dry cough, rhinorrhea (nasal discharge), headache, muscle pain, and achiness.〔〔Matsuzaki Y, Katsushima N, Nagai Y, Shoji M, Itagaki T, Sakamoto M, Kitaoka S, Mizuta K, Nishimura H. 2006. “Clinical Features of Influenza C Virus Infection in Children” The Journal of Infectious Diseases. 193(9):1229-1235.〕 The virus may lead to more severe infections such as bronchitis and pneumonia.〔 After an individual becomes infected, the immune system develops antibodies against that infectious agent. This is the body’s main source of protection.〔 Most children between five and ten years old have already produced antibodies for influenza virus C.〔 As with all influenza viruses, type C affects individuals of all ages, but is most severe in young children, the elderly and individuals with underlying health problems.〔〔Ballada D, Biasio LR, Cascio G, D’Alessandro D, Donatelli I, Fara GM, Pozzi T, Profeta ML, Squarcione S, Ricco D, Todisco T, Vacca F. 1994. “Attitudes and Behavior of Health Care Personnel Regarding Influenza Vaccination” European Journal of Epidemiology. 10(1):63-68.〕 Young children have less prior exposure and have not developed the antibodies and the elderly have less effective immune systems.〔 Influenza virus infections have one of the highest preventable mortalities in many countries of the world.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Influenzavirus C」の詳細全文を読む スポンサード リンク
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