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In epidemiology, an outbreak is a sudden increase in occurrences of a disease in a particular time and place. It may affect a small and localized group or impact upon thousands of people across an entire continent. Two linked cases of a rare infectious disease may be sufficient to constitute an outbreak. Outbreaks may also refer to epidemics, which affect a region in a country or a group of countries, or pandemics, which describe global disease outbreaks. ==Outbreak investigation== When investigating disease outbreaks, the epidemiology profession has developed a number of widely accepted steps. As described by the Centers for Disease Control and Prevention, these include the following:〔(Steps of an Outbreak Investigation ), EXCITE | Epidemiology in the Classroom | Outbreak Steps〕 * Verify the diagnosis related to the outbreak * Identify the existence of the outbreak (Is the group of ill persons normal for the time of year, geographic area, etc.?) * Create a case definition to define who/what is included as a case * Map the spread of the outbreak using Information technology as diagnosis is reported to insurance * Develop a hypothesis (What appears to be causing the outbreak?) * Study hypothesis (collect data and perform analysis) * Refine hypothesis and carry out further study * Develop and implement control and prevention systems * Release findings to greater communities Outbreak debriefing and review has also been recognized as an additional final step and iterative process by the Public Health Agency of Canada.〔(【引用サイトリンク】title=Canada’s Food-borne Illness Outbreak Response Protocol (FIORP) 2010: To guide a multi-jurisdictional response )〕 ==Types== There are several outbreak patterns, which can be useful in identifying the transmission method or source, and predicting the future rate of infection. Each has a distinctive epidemic curve, or histogram of case infections and deaths.〔() 〕 * Common source – All victims acquire the infection from the same source (e.g. a contaminated water supply).〔(Glossary of Epidemiology Terms ), Cdc.gov (2007-04-25). Retrieved on 2010-11-25.〕 * * Continuous source – Common source outbreak where the exposure occurs over multiple incubation periods * * Point source – Common source outbreak where the exposure occurs in less than one incubation period〔(Glossary of Epidemiology Terms ). Cdc.gov (2007-04-25). Retrieved on 2010-11-25.〕 * Propagated – Transmission occurs from person to person.〔(Glossary of Epidemiology Terms ). Cdc.gov (2007-04-25). Retrieved on 2010-11-25.〕 Outbreaks can also be: * Behavioral risk related (e.g., sexually transmitted diseases, increased risk due to malnutrition)〔() 〕 * Zoonotic – The infectious agent is endemic to an animal population. Patterns of occurrence are: * Endemic – a communicable disease, such as influenza, measles, mumps, pneumonia, colds, smallpox, which is characteristic of a particular place, or among a particular group, or area of interest or activity. * Epidemic – when this disease is found to infect a significantly larger number of people at the same time than is common at that time, and among that population, and may spread through one or several communities. * Pandemic – occurs when an epidemic spreads worldwide. 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「Outbreak」の詳細全文を読む スポンサード リンク
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