短语讲解：

1. But the health agency ruled out a ban on travel or trade in affected areas.

rule out 用直线划掉; 宣布…不可能，排除…的可能性
例句：So that could rule out robbery as a motive.
这样就可以排除抢劫的动机。

2. At this time, there is no treatment or vaccine for the Zika virus.

at this time 此时此刻
例句：Many writers at this time held rigidly dogmatic views.
这时期有很多作家固执己见。