有同學問我這幾個字的區別:
1. Epidemic (n.) refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area.
流行、傳染病(epidemic)是指某種疾病病例數的增加，通常為突發的，超出該地區人口的一般預期程度。
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2. Outbreak (n.) carries the same definition of epidemic, but is often used for a more limited geographic area.
爆發(outbreak)與流行、傳染(epidemic)相同定義，但通常用於更侷限的地理區域。
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3. Endemic (n.) refers to the constant presence and/or usual prevalence of a disease or infectious agent in a population within a geographic area.
地方性的、區內流行病(endemic)是指疾病或傳染原在一個地理區域內的人口中持續存在和/或普遍流行。
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4. Cluster (n.) refers to an aggregation of cases grouped in place and time that are suspected to be greater than the number expected, even though the expected number may not be known.
群聚(cluster)指的是一個以地點時間分組的病例的集合，這些病例被懷疑大於預期的數量，即使預期的數量可能未知。
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5. Pandemic (n.) refers to an epidemic that has spread over several countries or continents, usually affecting a large number of people.
大流行病(pandemic)是指已蔓延到多個國家或大洲的流行病(epidemic)，通常影響著非常多人。
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The use of outbreak and epidemic overlap in some instances!Don’t forget our class on health (U18): https://ericvocab.teachable.com/courses/ericvocab_full/lectures/12016185
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Image source: http://www.securitymanagers.net/epidemic-vs-pandemic/