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Influenza prevention involves taking steps that one can use to decrease their chances of contracting flu viruses, such as the Pandemic H1N1/09 virus, responsible for the 2009 flu pandemic. ==Influenza transmission== People who contract influenza are most infective between the second and third days after infection, and infectivity lasts for around ten days. Children are much more infectious than adults and shed virus from just before they develop symptoms until two weeks after infection.〔 The transmission of influenza can be modeled mathematically, which helps predict how the virus will spread in a population. Influenza can be spread in three main ways: *by direct transmission (when an infected person sneezes mucus directly into the eyes, nose or mouth of another person); *the airborne route (when someone inhales the aerosols produced by an infected person coughing, sneezing or spitting); *through hand-to-eye, hand-to-nose, or hand-to-mouth transmission,〔(Center for Disease Control and Prevention: "QUESTIONS & ANSWERS: Novel H1N1 Flu (Swine Flu) and You" ) Retrieved December 13, 2009〕 either from contaminated surfaces or from direct personal contact such as a hand-shake. The relative importance of these three modes of transmission is unclear, and they may all contribute to the spread of the virus. In the airborne route, the droplets that are small enough for people to inhale are 0.5 to 5 µm in diameter and inhaling just one droplet might be enough to cause an infection.〔 Although a single sneeze releases up to 40,000 droplets, most of these droplets are quite large and will quickly settle out of the air.〔 How long influenza survives in airborne droplets seems to be influenced by the levels of humidity and UV radiation: with low humidity and a lack of sunlight in winter probably aiding its survival.〔 As the influenza virus can persist outside of the body, it can also be transmitted by contaminated surfaces such as banknotes, doorknobs, light switches and other household items.〔(【引用サイトリンク】title=Influenza: Viral Infections: Merck Manual Home Edition ) 〕 The length of time the virus will persist on a surface varies, with the virus surviving for one to two days on hard, non-porous surfaces such as plastic or metal, for about fifteen minutes from dry paper tissues, and only five minutes on skin. However, if the virus is present in mucus, this can protect it for longer periods.〔 Avian influenza viruses can survive indefinitely when frozen.〔(【引用サイトリンク】title=Influenza Factsheet ) p. 7〕 They are inactivated by heating to 56 °C (133 °F) for a minimum of 60 minutes, as well as by acids (at pH <2).〔 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「Influenza prevention」の詳細全文を読む スポンサード リンク
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