C.O.
the BRAT diet (bananas, rice, applesauce, toast) will help...most importantly bananas - as diahrrea and stomach flus deplete our system of potassium.
if you can get a sample of it - I would - like keep a clear plastic wrap over part of the toilet so you can catch some of it to take to your pediatrician - that would be a good thing...in my opinion.