Their enthusiasm was 'infectious'. [='contagious']
viruses and other 'infectious' agents
an acute 'infectious' illness
(..) is because of the wonderful online videos that Emil and Karen have been putting together. We just love going viral. So do infectious diseases. Right, uh, so I guess Men Now really is taking off. I guess you'll just have to keep all those profits to yourself. (..)2016 TvShow: Bones Title: The Murder of the Meninist Season: 11 Episode 12