来自《耶鲁大学开放课程：生物医学工程探索第1集第1集》

In 1665, 93% of the people that died in that year

在一六六五年死亡的总人数中
died of infectious diseases.

百分之九十三都是死于感染性疾病
In contrast, if you look at a U.S.City,

相反我们看美国的城市
ten years ago in 1997 for example,

例如在十年前即一九九七年
then people still died

人们还是会死亡
but they didn't die predominantly from infectious diseases.

但是最主要的死因不再是感染性疾病
They died from other things:

他们死于一些其他的原因
only 4% died from infectious diseases.

感染性疾病只占百分之四
So one of the reasons there is a huge increase in life span is

寿命范围显著增长的一个原因是
because people aren't dying of things

人们不再死于
that they would have in prior years.

以前那些致死的东西
Why the change in infectious diseases?

为什么感染性疾病致死率发生了变化