The drug prevents the virus from replicating itself.

这种药能防止病毒复制。

《牛津词典》

The drug attenuates the effects of the virus.

这药能减轻病毒的危害。

《牛津词典》

There are many different strains of flu virus.

有许多不同类型的流感病毒。

《柯林斯英汉双解大词典》

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

耶鲁公开课 - 生物医学工程探索课程节选

The virus is not killed so It's a live virus, which is actually going to infect your intestinal system and reproduce.

病毒没有被杀死,那么它就是活性病毒,也就意味着它将会,侵入你的肠道系统并且会繁殖

耶鲁公开课 - 生物医学工程探索课程节选

So, that was a naturally occurring attenuated virus that could be produced into a vaccine that didn't cause the disease.

因为天花病毒存在天然的衰减病毒,这种衰减病毒可以用来,直接生产不致病的疫苗

耶鲁公开课 - 生物医学工程探索课程节选