My son has had diarrhea and vomiting on and off for 6 days. no fever, can only keep down water, hungry! virus or something else?

Vomiting/Diarrhea: While the likely cause is viral, after 6 days he should be seen by his physician.

GI problems: Often, with prolonged gastro-intestnal problems, the culprit is often not viral but bacterial in nature. There is also the possibility of an underlying problem (appendicitis). Since children have less fluid and electrolyte reserves than adults, prolonged nausea/vomiting can quickly lead to dehydration. It is important to get your child to the pediatrician for accurate diagnosis/treatment.