So, it's awkward to have to wait for a cow to get infected before you can vaccinate a population.

在给人们预防接种之前,你只有干等着,直到有一头奶牛感染了病毒才行

耶鲁公开课 - 生物医学工程探索课程节选

So look, why am I justified in believing in germs, various kinds of viruses that I can't see, or bacteria or what have you, that I can't see?

所以,我为什么相信微生物,相信各种肉眼无法看到的病毒,细菌等诸如此类我看不到的东西确实存在

耶鲁公开课 - 死亡课程节选