epidemic和pandemic的区别
epidemic和pandemic的区别介绍如下：
epidemic是流行病。
pandemic是全球大流行病。
在老外的日常用语里，他们对流行病第一反应就是epidemic这个词，而pandemic能让他们想到的是非常严重传播非常广泛的流行病，比如1918年席卷全球导致至少5000万人死亡的西班牙大流感。
你要真问他们epidemic和pandemic严格区分的标准是什么，他们也说不出来，只知道pandemic比epidemic更严重，就像catastrophe比disaster要严重一样。
美国疾病预防控制中心（USCDC）对流行病传播的严重程度从低到高有以下五个级别：
Sporadic（零星的）: When a disease occurs infrequently and irregularly.
Endemic（地方性的）: A constant presence and/or usual prevalence of a disease or infection within a geographic area.
Hyperendemic（高度地方性的）：is a situation in which there are persistent, high levels of disease occurrence.
Epidemic（流行的）: A sudden increase in the number of cases of a disease—more than what's typically expected for the population in that area.
Pandemic（大流行的）: An epidemic that has spread over several countries or continents, affecting a large number of people.
