We know now that it's caused by a related virus, called vaccinia, remember the virus that causes smallpox is called variola.

我们现在知道这病由一种相关的病毒引起,这种病毒叫牛痘病毒,想想天花病毒也被叫做牛痘病毒

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And he produced a fluid from cowpox lesions, so these were these lesions, these skin lesions on cows.

他生产出一种取自牛痘,即牛皮肤上的瘢痕的液体

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And so in the 1940s, a group of people led by Collier started to develop a large scale production method for making a reliable source of vaccinia virus.

在二十世纪四十年代,科利尔带领一群人开始研究,一种大规模的生产方法,这种方法能制得牛痘病毒的可靠来源

耶鲁公开课 - 生物医学工程探索课程节选