他们的笑容感染了周围的人。

Their smiles are ___contagious.

麻疹是一种高度传染性的疾病，通过空气传播。

Measles is a highly ___contagious disease that spreads through the air.

他的积极态度很有感染力，整个团队都受到了鼓舞。

His positive attitude was so ___contagious that the whole team felt motivated.