Hi, Welcome to health care magic, Fever,vomiting and diarrhea are the symptoms of stomach flu which is likely to be due to acute bacterial gastroenteritis or viral gastroenteritis etc. Your child must undergo routine blood count,electrolytes with clinical examination of abdomen or ultrasound of abdomen. He will require antibiotics (quinolones or cephalosporins or antiprotozoals etc.) with antiemetic, antispasmodics and anti-inflammatories with prebiotics and probiotics. There might be great need of fluid and electrolyte balance in body. So,you must take him to the physician or visit ER for immediate treatment rather than giving any symptomatic treatment or waiting. Thanks and regards,