The baby suddenly fever, no other clinical symptoms, first consider the existence of upper respiratory tract viral infection or the existence of bacterial infection in the body. 1. upper respiratory tract viral infections: upper respiratory tract viral infections, part of the baby may not have nasal congestion, runny nose, sore throat and other symptoms, only manifested as simple fever, at this time, pay attention to monitor the body temperature, drink more water. 2. Bacterial infections: the existence of bacterial infections in babies, the early may not have obvious clinical symptoms simply manifested as fever, such as acute tonsillitis, acute bronchitis, acute pneumonia, etc., at this time need to be combined with the blood routine, the relevant signs to make a judgment. If the fever persists without relief, it is recommended to consult a regular hospital in time to find out the cause.