Need to vent

I am so mad right now! Came to my in-laws who I love for Easter with my husband and almost 12 week old daughter. Find out my sister n law brought her 3 kids and one of them has impetigo! Like seriously why would you not tell me ahead of time! If I would have known that I would have never of came! How rude is it to risk getting my baby sick. I am almost in tears right now thinking my baby might get sick now.