Once people get Zika, they won't get it again.

一旦人们感染了寨卡病毒，他们不会再次感染。

Once it had landed safely on the ground, the cat felt smug.

一旦安全着陆，猫就感到得意。

Once matter has decayed, it can't go back to the way it used to be.

一旦物质腐烂，它就不能恢复原样。

Once people had money to spend, they used markets to buy things.

一旦人们有了钱，他们就用市场来购买东西。

"Anyway, once you've seen one crazy fish, you've seen them all."

“反正，一旦你看到一条疯狂的鱼，你就见过所有的了。”