<s>[INST] My son is almost 3 years old-he has been vomiting on and off for a little over 2 weeks.  Occasional diarrhea-every other day-he was usually very active-the last day or 2 seems more tired than usual. We took him his pediatrician today and he said it was a virus-he coughs right before he vomits-I was thinking post nasal drip. Isn't too long to be a virus?  What are your thoughts? No fever. [/INST] Sometimes, viruses take a longer time to clear. However, to be sure, you should do his stool exam and his blood counts so that, if needed, he can be started on antibiotics. Post-nasal drip is unlikely in a three-year old child. The more likely cause of his cough are adenoids. </s>