16 month old with diarrhea, what's causing it? & what can I do to help her feel better?

We all know that kids put everything in there mouths and germs are everywhere, no matter how clean you are. Im like a germ freak and 2 months ago my 2 year old had real bad diarrhea for 5 days(ugh it was awful!) Any who we had no idea how he caught it. My husband and I are constantly washing our boys hands, cleaning there toys etc. The doc was like it just happens. That it was the stomach flu. We gave him jello, ginger ale(that was a rare treat for him, that he loved LOL:)) saltine crackers with cheese, yogurt. Im sure something else but i don't remember. Give plenty of fluids to keep her hydrated, water alone will not due and she can still dehydrate with that. She needs electrolytes, sodium. Stay home and it will get better. If it gets worse don't hesitate to call the pediatricians office for more advice. Good luck and hope your lil one is feeling better in no time.