As the new coronavirus continues to spread around the world, the words epidemic¹ and pandemic are showing up in news reports more often than they usually do. While the terms are closely related, they don't refer to the same thing.

新冠病毒持续在全球传播之际，epidemic和pandemic这两个词比往常更频繁地在新闻报道中出现。尽管这两个词很相近，但二者指的不是同一种东西。

As the Association for Professionals in Infection Control and Epidemiology (APIC) explains on its website, "an epidemic occurs when an infectious disease spreads rapidly to many people." Usually, what precedes an epidemic is an outbreak, or "a sudden rise in the number of cases of a disease." An outbreak can affect a single community or several countries, but it's on a much smaller scale than an epidemic.

感染控制和流行病学专业人员协会在网站上解释道：“当一种传染性疾病迅速传播给许多人时，就被称为epidemic。”通常，epidemic发生之前会有outbreak（疾病暴发），即“某种疾病案例的突然增加”。Outbreak可能影响到单个社区或几个国家，但规模比epidemic小得多。

If an epidemic can't be contained and keeps expanding its reach, public health officials might start calling it a pandemic, which means it's affected² enough people in different areas of the world to be considered a global outbreak. In short, a pandemic is a worldwide epidemic. It infects more people, causes more deaths, and can also have widespread social and economic repercussions³. The spread of the Spanish influenza⁴ from 1918 to 1919, which killed between 20 and 40 million people around the world, was a pandemic; more recently, the H1N1 influenza created a pandemic in 2009.

如果一场epidemic不能被控制住，还在不断蔓延，公共卫生官员可能就要开始称之为pandemic，意思是这场流行病已经影响到世界不同地区足够多的人，到了全球性暴发的程度。简而言之，pandemic就是全球性的流行病。Pandemic感染的人更多，导致的死亡人数更多，还可能对社会和经济造成广泛的影响。1918年到1919年的西班牙流感在全世界导致2000万至4000万人丧生，这种流行病属于pandemic；离现在更近的2009年的甲型流感也是pandemic。

Here's where it gets a little tricky⁵: There's no cut-and-dried classification system for outbreaks, epidemics⁶, and pandemics.

但是微妙之处在于，outbreak、epidemic和pandemic三者之间没有既成的区分体系。

The WHO warned on Monday against using the term "pandemic" to describe the current outbreak.

世界卫生组织2月24日曾警告称，本次新冠肺炎疫情不能用pandemic来形容。

"It really is borderline semantics, to be honest with you," Anthony Fauci, director of the National Institute of Allergy⁷ and Infectious Diseases, told CNN earlier this month. "I think you could have people arguing each end of it. Pandemics mean different things to different people."

美国国家过敏和传染病研究所的所长安东尼·福奇本月早些时候告诉CNN说：“老实说，这确实是边界语义学。我想你会听到人们各执一词。不同的人对pandemic有不同的理解。”