Flu season - wikipedia Flu season For the Parks and Recreation episode, see Flu Season ( Parks and Recreation ). The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. You may improve this article, discuss the issue on the talk page, or create a new article, as appropriate. ( March 2010 ) Influenza ( Flu ) Types Avian A / H5N1 subtype Canine Equine Swine A / H1N1 subtype Vaccines 2009 pandemic Pandemrix Fluzone Influvac Live attenuated Optaflu Treatment Amantadine Laninamivir Oseltamivir Peramivir Rimantadine Umifenovir Vitamin D Zanamivir Pandemics 2009 swine 1968 -- 1969 Hong Kong 1957 Asian flu 1918 Outbreaks 2015 United States H5N2 outbreak 2014 Kerala 2008 West Bengal 2007 Bernard Matthews H5N1 2007 Australian equine 2006 H5N1 India 1976 swine flu See also Flu season Influenza evolution Influenza research Influenza - like illness Vaccine reformulations Flu season is an annually recurring time period characterized by the prevalence of outbreaks of influenza ( flu ). The season occurs during the cold half of the year in each hemisphere. Influenza activity can sometimes be predicted and even tracked geographically. While the beginning of major flu activity in each season varies by location, in any specific location these minor epidemics usually take about 3 weeks to peak and another 3 weeks to significantly diminish immediately. Contents 1 Cause 2 Timing 3 Flu vaccinations 4 Health conditions likely to cause complications 4.1 Diabetes 4.2 Asthma / COPD 4.3 Cancer 4.4 HIV / AIDS 5 Cost 6 Notable occurrences 7 See also 8 Sources and notes 9 Further reading 10 External links Cause Main article : Influenza Three virus families, Influenzavirus A, B, and C are the main infective agents that cause influenza. During periods of cooler temperature, influenza cases increase roughly tenfold or more. Despite higher incidence of manifestations of the flu during the season, the viruses are actually transmitted throughout populations all year round. Each annual flu season is normally associated with a major influenzavirus subtype. The associated subtype changes each year, due to development of immunological resistance to a previous year 's strain ( through exposure and vaccinations ), and mutational changes in previously dormant viruses strains. The exact mechanism behind the seasonal nature of influenza outbreaks is unknown. Some proposed explanations are : People are indoors more often during the winter, they are in close contact more often, and this promotes transmission from person to person. A seasonal decline in the amount of ultraviolet radiation may reduce the likelihood of the virus being damaged or killed by direct radiation damage or indirect effects ( i.e. ozone concentration ) increasing the probability of infection. Cold temperatures lead to drier air, which may dehydrate mucous membranes, preventing the body from effectively defending against respiratory virus infections. Viruses are preserved in colder temperatures due to slower decomposition, so they linger longer on exposed surfaces ( doorknobs, countertops, etc. ). In nations where children do not go to school in the summer, there is a more pronounced beginning to flu season, coinciding with the start of public school. It is thought that the day care environment is perfect for the spread of illness. Vitamin D production from Ultraviolet - B in the skin changes with the seasons and affects the immune system. Research in guinea pigs has shown that the aerosol transmission of the virus is enhanced when the air is cold and dry. The dependence on aridity appears to be due to degradation of the virus particles in moist air, while the dependence on cold appears to be due to infected hosts shedding the virus for a longer period of time. The researchers did not find that the cold impaired the immune response of the guinea pigs to the virus. Research done by National Institute of Child Health and Human Development ( NICHD ) in 2008 found that the influenza virus has a `` butter - like coating ''. The coating melts when it enters the respiratory tract. In the winter, the coating becomes a hardened shell ; therefore, it can survive in the cold weather similar to a spore. In the summer, the coating melts before the virus reaches the respiratory tract. Timing Seasonal variation in deaths due to influenza or pneumonia in 122 U.S. cities, vs. other causes. In the United States, the flu season is considered October through May. It usually peaks in February. In Australia, the flu season is considered May to October. It usually peaks in August. Flu seasons also exist in the tropics and subtropics, but are usually less sharply defined. In Hong Kong, which has a humid subtropical climate, the flu season runs from December to March, in the winter and early spring. Flu vaccinations Main article : Influenza vaccine Flu vaccinations have been used to diminish the effects of the flu season ; pneumonia vaccinations additionally diminishes the effects and complications of flu season. Since the Northern and Southern Hemisphere have winter at different times of the year, there are actually two flu seasons each year. Therefore, the World Health Organization ( assisted by the National Influenza Centers ) makes two vaccine formulations every year ; one for the Northern, and one for the Southern Hemisphere. According to the U.S. Department of Health, a growing number of large companies provide their employees with seasonal flu shots, either at a small cost to the employee or as a free service. The annually updated trivalent influenza vaccine consists of hemagglutinin ( HA ) surface glycoprotein components from influenza H3N2, H1N1, and B influenza viruses. The dominant strain in January 2006 was H3N2. 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. Health conditions likely to cause complications Pediatric deaths from influenza 2011 - 2014 - a small fraction of the overall number of flu deaths in the U.S. each year, most of which occur in elderly people. Medical conditions that compromise the immune system increase the risks from flu. Diabetes Millions of people have diabetes. When blood sugars are not well controlled, diabetics can quickly develop a wide range of complications. Diabetes results in elevated blood sugars in the body, and this environment allows viruses and bacteria to thrive. If blood sugars are poorly controlled, a mild flu can quickly turn severe, leading to hospitalization and even death. Uncontrolled blood sugars suppresses the immune systems and generally lead to more severe cases of the common cold or influenza. Thus, it has been recommended that diabetics are vaccinated against flu, before the start of the flu season. Asthma / COPD It is recommended that asthmatics and COPD patients be vaccinated against flu before the flu season. People with asthma can develop life - threatening complications from influenza and the common cold viruses. Some of these complications include pneumonias, acute bronchitis, and acute respiratory distress syndrome. Each year flu related complications in the USA affect close to 100,000 asthmatics, and millions more are seen in the emergency room because of severe shortness of breath. It is recommended that asthmatics are vaccinated between October and November, before the peak of the flu season. Flu vaccine works by boosting the body 's immune system and takes about 2 weeks to become effective. Cancer People with cancer usually have a suppressed immune system. Moreover, many cancer patients undergo radiation therapy and potent immunosuppressive medications, which further suppresses the body 's ability to fight off infections. Everyone with cancer is highly susceptible and is at risk for complications from flu. People with cancer or a history of cancer should receive the seasonal flu shot. Flu vaccination is also strict for lung cancer patients, as cancer leads to complications of pneumonia and bronchitis. People with cancer should not receive the nasal spray vaccine. The flu shot is made up of inactivated ( killed ) viruses, and the nasal spray vaccines are made up of live viruses. The flu shot is safer for those with a weakened immune system. Those who have received cancer treatment such as chemotherapy and / or radiation therapy within the last month, or have a blood or lymphatic form of cancer should call their doctor immediately if they suspect they may have flu. HIV / AIDS Individuals who acquire the human immune deficiency virus ( HIV ) are very prone to a variety of infections. HIV has a tremendous capacity to destroy the body 's immune system and this makes one prone to not only viral infections but also bacterial, fungal, and protozoa disorders. People with HIV are at an increased risk of serious flu - related complications. Many reports have shown that individuals with HIV can develop serious pneumonias which need hospitalization and aggressive antibiotic therapy. Moreover, people with HIV have a longer flu season and are at a high risk of death. Vaccination with the flu shot has been shown to boost the immune system and protect against the seasonal flu in some patients with HIV ; individuals who have HIV should only get vaccinated with the inactivated influenza vaccine. Any HIV patient who has been exposed to other people with influenza should see a physician to determine if there is a need for anti viral medications. Cost During the 2011 - 2014 seasons, flu - like illnesses have typically accounted for 6 % of outpatient visits at the peak of the season in the United States. The cost of a flu season in lives lost, medical expenses and economic impact can be severe. `` In the United States of America, for example, recent estimates put the cost of influenza epidemics to the economy at US $ 71 - 167 billion per year. '' A recent study estimated that in the United States, annual influenza epidemics result in approximately 600,000 life - years lost, 3 million hospitalized days, and 30 million outpatient visits, resulting in medical costs of $10 billion annually. According to this study, lost earnings due to illness and loss of life amounted to over $15 billion annually and the total economic burden of annual influenza epidemics amounts to over $80 billion. Also, in the US the flu season usually accounts for 200,000 hospitalizations and 41,000 deaths. Because the mortality rate of the H1N1 `` swine flu '' is lower than common flu strains, this number was actually lower in 2009. According to an article in Clinical Infectious Diseases, published in 2011, the estimated health burden of 2009 Pandemic Influenza A ( H1N1 ), between April 2009 to April 2010, was `` approximately 60.8 million cases ( range : 43.3 -- 89.3 million ), 274,304 hospitalizations ( 195,086 -- 402,719 ), and 12,469 deaths ( 8,868 -- 18,306 ) '' `` in the United States due to pH1N1. '' Notable occurrences The 2012 -- 13 flu season was particularly harsh in the United States, where the majority of states were reporting high rates of influenza - like illness. The Centers for Disease Control reported that the available flu vaccine was 60 % effective. It further recommended that all persons over age 6 months get the vaccine. See also Influenza Influenza vaccine Bird flu Human flu Swine flu Horse flu Dog flu Freshers ' flu 2012 -- 13 flu season 2013 -- 14 flu season 2014 -- 15 flu season 2015 - 16 flu season 2016 - 17 flu season Sources and notes Jump up ^ National Institute of Allergy and Infectious Diseases ( NIAID ) Factsheet ^ Jump up to : Lowen, AC ; Mubareka, S ; Steel, J ; Palese, P ( October 2007 ). `` Influenza virus transmission is dependent on relative humidity and temperature '' ( PDF ). PLoS Pathogens. 3 ( 10 ) : e151. PMC 2034399. PMID 17953482. doi : 10.1371 / journal. ppat. 0030151. Jump up ^ Shaman J, Kohn M ( March 2009 ). `` Absolute humidity modulates influenza survival, transmission, and seasonality ''. Proc. Natl. Acad. Sci. U.S.A. 106 ( 9 ) : 3243 -- 8. PMC 2651255. PMID 19204283. doi : 10.1073 / pnas. 0806852106. Jump up ^ Shaman J, Pitzer VE, Viboud C, Grenfell BT, Lipsitch M ( February 2010 ). Ferguson, Neil M., ed. `` Absolute humidity and the seasonal onset of influenza in the continental United States ''. PLoS Biol. 8 ( 2 ) : e1000316. PMC 2826374. PMID 20186267. doi : 10.1371 / journal. pbio. 1000316. CS1 maint : Multiple names : authors list ( link ) Jump up ^ Cannell, JJ ; Vieth R ; Umhau J ; Holick M ; Grant W ; Madronich S ; Garland C ; Giovannucci E ( 2006 ). `` Epidemic influenza and vitamin D ''. Epidemiol Infect. 134 ( 6 ) : 1129 -- 40. PMC 2870528. PMID 16959053. doi : 10.1017 / S0950268806007175. Jump up ^ Cannel, JJ ; Zasloff M ; Garland CF ; Scragg R ; Giovannucci E ( 2008 ). `` On the epidemiology of influenza ''. Virol J. 5 ( 29 ) : 29. PMC 2279112. PMID 18298852. doi : 10.1186 / 1743 - 422X - 5 - 29. Jump up ^ Adit, G ; Mansbach J ; Camargo C ( 2009 ). `` Association Between Serum 25 - Hydroxyvitamin D Level and Upper Respiratory Tract Infection in the Third National Health and Nutrition Examination Survey ''. Arch Intern Med. 169 ( 4 ) : 384 -- 90. PMC 3447082. PMID 19237723. doi : 10.1001 / archinternmed. 2008.560. Jump up ^ Polozov, IV ; Bezrukov L ; Gawrisch K ; Zimmerberg J ( 2008 ). `` Progressive ordering with decreasing temperature of the phospholipids of influenza virus ''. Nat Chem Biol. 4 ( 4 ) : 248 -- 55. PMID 18311130. doi : 10.1038 / nchembio. 77. Jump up ^ CDC Questions and Answers 2010 - 01 - 27, Retrieved 2010 - 08 - 10. Jump up ^ CDC : The Flu Season Jump up ^ Australian Department of Health and Ageing. Australian influenza report 2011 Retrieved 2012 - 06 - 03 Jump up ^ Florence H.Y. Yap ; Pak - Leung Ho ; et al. ( June 2004 ). `` Excess hospital admissions for pneumonia, chronic obstructive pulmonary disease, and heart failure during influenza seasons in Hong Kong ''. Journal of Medical Virology. 73 ( 4 ) : 617 -- 623. doi : 10.1002 / jmv. 20135. Jump up ^ Chit - Ming Wong ; King - Pan Chan ; Anthony Johnson Hedley ; J.S. Malik Peiris ( December 2004 ). `` Influenza - associated mortality in Hong Kong ''. Clinical Infectious Diseases. 39 ( 11 ) : 1611 -- 1617. doi : 10.1086 / 425315. Jump up ^ Daum LT, Shaw MW, Klimov AI, Canas LC, Macias EA, Niemeyer D, Chambers JP, Renthal R, Shrestha SK, Acharya RP, Huzdar SP, Rimal N, Myint KS, Gould P ( August 2005 ). `` Influenza A ( H3N2 ) outbreak, Nepal ''. Emerging Infect. Dis. 11 ( 10 ) : 1186 -- 91. PMC 3320503. PMID 16102305. doi : 10.3201 / eid1108. 050302. Jump up ^ Bird Flu : Threat or Menace ? Why avian sniffles need not ruffle our feathers... too much Ronald Bailey October 19, 2005 Jump up ^ Lawrence K. Altman ( January 15, 2006 ). `` This Season 's Flu Virus Is Resistant to 2 Standard Drugs ''. The New York Times. Retrieved 30 October 2006. Jump up ^ flu.gov : Diabetes and the Flu Jump up ^ CDC brochure on flu vaccination for diabetics Jump up ^ Flu Season Overview North Carolina Immunization portal. Retrieved 2010 - 02 - 09 Jump up ^ Centers for Disease Control and Prevention. `` HIV / AIDS and the Flu '' 2010 - 02 - 09. Jump up ^ Centers for Disease Control and Prevention. `` Cancer and the Flu '' Retrieved 2012 - 11 - 05 Jump up ^ Flu Season 2005 - 2006 : Questions & Answers MedicineNet. Retrieved 2010 - 02 - 09 Jump up ^ WHO Influenza Overview http://www.who.int/mediacentre/factsheets/2003/fs211/en/ Jump up ^ Molinari, Ortega - Sanchez, Messonnier, Thompson, Wortley, Weintraub, Bridges The annual impact of seasonal influenza in the US : Measuring disease burden and costs doi : 10.1016 / j. vaccine. 2007.03. 046 PMID 17544181 Jump up ^ Sundar S. Shrestha ; David L. Swerdlow ; Rebekah H. Borse ; Vimalanand S. Prabhu ; Lyn Finelli ; Charisma Y. Atkins ; Kwame Owus - Edusei ; Beth Bell ; Paul S. Mead ; Matthew Biggerstaff ; Lynnette Brammer ; Heidi Davidson ; Daniel Jernigan ; Michael A. Jhung ; Laurie A. Kamimoto ; Toby L. Merlin ; Mackenzie Nowell ; Stephen C. Redd ; Carrie Reed ; Anne Schuchat ; Martin I. Meltzer ( 2011 ). `` Estimating the Burden of 2009 Pandemic Influenza A ( H1N1 ) in the United States ( April 2009 -- April 2010 ) ''. Clinical Infectious Diseases. 52 ( suppl 1 ) : S75 -- S82. PMID 21342903. doi : 10.1093 / cid / ciq012. Jump up ^ `` Flu Season Continues ; Severity Indicators Rise ''. Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases ( NCIRD ). January 17, 2014. Retrieved 24 January 2014. Jump up ^ Szabo, Liz ; Vergano, Dan ; Weise, Elizabeth ( 11 January 2013 ). `` Flu widespread in 47 states ''. USA Today. McLean, VA : Gannett. ISSN 0734 - 7456. Retrieved 11 January 2013. Jump up ^ Szabo, Liz ( 11 January 2013 ). `` Questions and Answers : Flu season hits U.S. ''. USA Today. McLean, VA : Gannett. ISSN 0734 - 7456. Retrieved 11 January 2013. ^ Jump up to : `` As the flu spreads across the country, Boston declares an emergency ''. Consumer Reports. 10 January 2013. Retrieved 10 January 2013. ^ Jump up to : `` Early Estimates of Seasonal Influenza Vaccine Effectiveness -- United States, January 2013 '' ( PDF ). cdc.gov. 11 January 2013. Retrieved 11 January 2013. Further reading CDC U.S. influenza season summary with weekly updates -- Contains about a dozen charts and graphs with extensive text External links Health - EU portal EU response to influenza European Commission - Public Health EU coordination on Pandemic ( H1N1 ) 2009 Influenza General topics Research Vaccine Treatment Genome sequencing Reassortment Superinfection Flu season Viruses Orthomyxoviridae Influenza A Influenza B Influenza C Influenza A virus subtypes H1N1 H1N2 H2N2 H2N3 H3N1 H3N2 H3N8 H5N1 H5N2 H5N3 H5N6 H5N8 H5N9 H6N1 H7N1 H7N2 H7N3 H7N4 H7N7 H7N9 H9N2 H10N7 H1N1 Pandemics 1918 ( `` Spanish flu '' ) 2009 ( `` swine flu '' ) Science 2009 A / H1N1 H5N1 Outbreaks Croatia ( 2005 ) India ( 2006 ) UK ( 2007 ) West Bengal ( 2008 ) Science Genetic structure Transmission and infection Global spread Vaccine clinical trials Human mortality Social impact Pandemic preparation Treatments Antiviral drugs Adamantane derivatives Amantadine Rimantadine Neuraminidase inhibitor Oseltamivir Laninamivir Peramivir Zanamivir Peramivir ( experimental ) Umifenovir Vaccines Live attenuated influenza vaccine Fluzone Pandemrix Pandemics and epidemics Pandemics `` Russian flu '' ( 1889 -- 1890 ) `` Spanish flu '' ( 1918 ) `` Asian flu '' `` Hong Kong flu '' ( 1968 ) `` Swine flu '' ( 2009 ) Epidemics `` Russian flu '' ( 1977 -- 1978 ) `` Fujian flu '' ( H3N2 ) Central Luzon H5N6 ( 2017 ) Non-human Mammals Canine Feline Equine 2007 Australian outbreak Swine Non-mammals Avian Fujian ( H5N1 ) Complications Acute bronchitis Bronchiolitis Croup Otitis media Pharyngitis Pneumonia Sinusitis Strep throat Related topics Influenza - like illness Viruses portal Medicine portal Retrieved from `` https://en.wikipedia.org/w/index.php?title=Flu_season&oldid=799699982 '' Categories : Influenza Seasonality Hidden categories : CS1 maint : Multiple names : authors list Articles with limited geographic scope from March 2010 USA - centric All articles with unsourced statements Articles with unsourced statements from November 2014 Talk Contents About Wikipedia Français Edit links This page was last edited on 9 September 2017, at 09 : 16. 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Question: when does the flu season begin and end
Answer: October through May