短语讲解：

1. Then they tested the antibody in pregnant mice infected with Zika.

infect with 把…传染给…; 使充满（某种感情）
例句：Go away, I don't want to infect you with my cold.
走开，我可不想把我的感冒传染给你。

2. Either you give it before somebody went into a high-risk area if they were traveling, or as soon as they knew they were pregnant and they were not infected already.

as soon as 一…就…; 一经
例句：As soon as we found this out, we closed the ward
我们一发现此事就关闭了病房。