A disease that is infectious can be caught by being near a person who has it. Compare contagious.
infectious diseases such as measles.
像麻疹这样的传染病。
These viruses are highly infectious.
这些病毒传染性很强。
If a feeling is infectious, it spreads to other people.
She radiates an infectious enthusiasm for everything she does.
她做的每件事都洋溢着一种极具感染力的热情。