"Stomach Flu" is not the flu.
It's norovirus or rotavirus, typically. http://www.cdc.gov/ncidod/dvrd/revb/gastro/faq.htm
Flu, or influenza is typically fever, body aches, cough, sore thread - not vomiting and diarrhea. http://www.cdc.gov/flu/about/disease/symptoms.htm
