My 4 year was diagnosed 3 weeks ago with influenza B which she has gotten better from that since then. She was hospitalized for 6 days with a low white blood count which they contributed to the flu. She has been home from the hospital for 3 weeks but off and on since then she has had a fever , stomach pain, vomiting , and diarehha. She s also very weak and sleeps all the time. Could this be something more serious than what the doctors are thinking.