Pandemic flu : a pandemic spreads around the world affecting a large number of people across many countries 大流行指疾病在全球多个国家肆虐，感染者众，并可在全球迅速扩散。
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An epidemic is a widespread outbreak of disease in a community or region . a pandemic spreads around the world affecting a large number of people across many countries . the speed with which the disease spreads around the world can be exceptionally high given the large volume of trade and people movement across boundaries 所谓流行病，就是指疾病在一个社群或地区中出现广泛爆发大流行则指疾病在全球多个国家肆虐，感染者众，而疾病在全球的扩散速度，也会因为大的跨境贸易与人口流动量而变得极为迅速。
