Have a 6 month old baby with temp of 39.8?

FEVER. 39.8c means 103.6f. Most fevers at this age are viral. The associated symptoms can be runny nose, cough, poor oral intake. Give a fever reducer when it is 101 f or above. If only fever with no other symptoms, UTI or other causes need to be ruled out. Take baby to the pediatrician for an exam. Make sure s/he drinks enough fluid.
Go to the Hospital. Fever in infants is an emergency. Please turn off health tap and get this child in to be seen by a physician urgently.