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A pandemic (from Greek πᾶν ''pan'' "all" and δῆμος ''demos'' "people") is an epidemic of infectious disease that has spread through human populations across a large region; for instance multiple continents, or even worldwide. A widespread endemic disease that is stable in terms of how many people are getting sick from it is not a pandemic. Further, flu pandemics generally exclude recurrences of seasonal flu. Throughout history there have been a number of pandemics, such as smallpox and tuberculosis. The Black Death was a devastating pandemic, killing over 75 million people. More recent pandemics include the HIV pandemic as well as the 1918 and 2009 H1N1 pandemics. == Definition and stages == A pandemic is an epidemic occurring on a scale which crosses international boundaries, usually affecting a large number of people. The World Health Organization (WHO) has a six-stage classification that describes the process by which a novel influenza virus moves from the first few infections in humans through to a pandemic. This starts with the virus mostly infecting animals, with a few cases where animals infect people, then moves through the stage where the virus begins to spread directly between people, and ends with a pandemic when infections from the new virus have spread worldwide and it will be out of control until we stop it.〔("Current WHO phase of pandemic alert" ), World Health Organization 2009〕 A disease or condition is not a pandemic merely because it is widespread or kills many people; it must also be infectious. For instance, cancer is responsible for many deaths but is not considered a pandemic because the disease is not infectious or contagious. In a virtual press conference in May 2009 on the influenza pandemic, Dr Keiji Fukuda, Assistant Director-General ''ad interim'' for Health Security and Environment, WHO said "An easy way to think about pandemic … is to say: a pandemic is a global outbreak. Then you might ask yourself: "What is a global outbreak"? Global outbreak means that we see both spread of the agent … and then we see disease activities in addition to the spread of the virus." In planning for a possible influenza pandemic, the WHO published a document on pandemic preparedness guidance in 1999, revised in 2005 and in February 2009, defining phases and appropriate actions for each phase in an aide memoir entitled ''WHO pandemic phase descriptions and main actions by phase''. The 2009 revision, including definitions of a pandemic and the phases leading to its declaration, were finalized in February 2009. The pandemic H1N1 2009 virus, was neither on the horizon at that time nor mentioned in the document〔(【引用サイトリンク】title=Pandemic influenza preparedness and response )〕〔(WHO pandemic phase descriptions and main actions by phase ) 〕 All versions of this document refer to influenza. The phases are defined by the spread of the disease; virulence and mortality are not mentioned in the current WHO definition, although these factors have previously been included. 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「pandemic」の詳細全文を読む スポンサード リンク
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