Now have made a genetic map of a cow.

VOA: special.2009.05.05

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

What if you're talking about a group of people that don't have any cows in their vicinity, let alone a sick cow?

万一你遇到一群人,他们附近连头奶牛都没有,更不用说受病毒感染的奶牛

耶鲁公开课 - 生物医学工程探索课程节选