来自《耶鲁大学开放课程：1600年后西方社会的流行病 第3集 第3集》
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So, the rat was extremely important.所以老鼠在这个传染链中是很重要的 -
The bacterium was spread in a third这个细菌在传染中的 -
major character,第三个主角 -
the flea,是跳蚤 -
a highly efficient vector for bubonic plague.它们是腺鼠疫的传染高效载体 -
The flea is naturally parasitic on warm-blooded animals.跳蚤一般寄生在温血动物身上 -
In a single feed it sucks up an amount of blood跳蚤一顿可以吸食 -
equal to its own weight.和它体重相当的血 -
I'm talking about something like a billion bacteria at a time.一次能够交换大约十亿细菌 -
And here we're looking at the slide of a flea这张图片是一只跳蚤 -
engorged with blood after a meal.在餐后被血胀满的样子 -
Now, once infected--你会为这些可怜的小东西感到遗憾的是