Flu- so worried!

Mia • M O M M Y 💕

So we went and saw my SIL Saturday and the next day my niece found out she has the flu with 103 temp. She was holding him and he was chewing on things he got from her. What’s the chance of my son getting the flu too? He’s sick now so I’m afraid his immune system is nothing. How long does it take to get symptoms from it after exposure? What are the symptoms in babies?