<s>[INST] my 9 year old daughter has been running a low fever 99/100, off and on for 3 weeks. she s tired more then shes not. no other symtoms except mentioned pain in stomache once and a headache once, in this last 3 weeks. took her to the doctors, he said lets wait it out, may be a virus, but to call if the fever gets 101 or more. should I be concerned and what could this fever be from? thank you [/INST] Hi, If she is otherwise okay, we need not worry. Usually viral fever should resolve by 5 days, but occasionally do persist for 2-3 weeks, as in conditions like IMN (mononucleosis). Still, if I were your treating doctor, as it is already 3 weeks, after a detailed examination to look for enlargement of lymph nodes, spleen or liver, I would prefer to get a complete blood count and a peripheral smear get done. This will help us to be sure that there is nothing else going on. Take care. Hope I have answered your question. Let me know if I can assist you further.  </s>