This is the 72nd most frequent Chinese word.
感染
"感染" means "infection" or "to infect/be infected."
Here, '感染' is used metaphorically to mean 'infect' in the sense of emotionally affecting others.
她的笑容感染了大家，每个人都感到很快乐。
Her smile was infectious to everyone, and everyone felt happy.
In this sentence, '感染' is used in the literal sense referring to being infected by a virus or disease.
医生采取了措施来防止病毒感染扩散。
The doctor took measures to prevent the spread of the virus infection.
Here, '感染' is used in a descriptive form (as '感染力') to denote the quality of influencing or moving others emotionally.