A sickness that can transmit and then dye into you (aka get inside you and infect you, via transmission) is a contagious disease. Everyone cover their mouths when they cough and sneeze, and please wash your hands, okay?
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
What is the most dangerous infectious disease in the world?