笑是有感染力的。

Laughing is contagious.

《柯林斯英汉双解大词典》

她不住地笑，没有停下来，笑声很有感染力。

She kept on laughing, didn't stop, and it was contagious.

youdao

她的微笑让我微笑。她的笑是有感染力的。她的心是纯洁的，是真的。最重要的是，我爱她是我的女儿。

Her smile makes me smile. Her laugh is infectious. Her heart is pure and true. Above all, I love that she is my daughter.

youdao