"Contagious enthusiasm" means when someone's excitement or passion for something spreads to others around them, making them feel excited and enthusiastic too. Full definition
I have trained before with others, but he brings fitness and nutritional expertise coupled with contagious enthusiasm like no other! (bradkolowichjr.com)
Participation and the emotional involvement which results from it produce a climate of contagious enthusiasm. (religion-online.org)
His sense of wonder and contagious enthusiasm make me smile so big! (theletteredcottage.net)