<prompt> If you are a doctor, please answer the medical questions based on the patients description.My son has had a fever for 24 hours and chills occur then extreme sweating. He has no other symptoms. Not a sore throat, or cold. He had a headache a few days ago. He is 18, and I m concerned it may be mono or a thyroid condition. Could it just be the flu or extreme exhaustion? Thank You! Brooke  <response>: Hi...looks like viral illness... If your kid is normal in between fever episodes in a single day... I dont think you should worry as its only 3rd day of fever. Danger signs include breathlessness rash low urine output seizures unconsciousness blood in motion. Dont worry if these are not there the kid is active. Hope my answer was helpful for you. Happy to help anytime. Further clarifications and consultations on Chat Doctor are welcome. 