One year old baby sudden fever without any symptoms, the cause of occurrence may be related to viral infections, urinary tract infections, intracranial infections, toddler’s acute rashes and so on. 1. viral infection: in general, the baby fever at the beginning, will be manifested as no symptoms, mostly caused by bacterial viral infections, due to the baby resistance is weak, easy to rhinovirus attack, can be manifested as a sudden fever. 2. urinary tract infection: urinary tract infection is often more insidious, and no obvious symptoms, if the baby suddenly fever, you can improve urine routine to assist in diagnosis. 3. intracranial infection: due to the baby’s blood-brain barrier development is not yet perfect, intracranial infection, often with atypical symptoms, will be manifested as meningeal irritation signs to, fever and other manifestations. 4. toddler rash: toddler rash belongs to the virus caused by the rash disease, occurring in young children, especially one year old babies, the onset of the initial period, did not show any symptoms of cold, fever for some time after the rash can appear, accompanied by a drop in body temperature performance. If a one-year-old baby suddenly fever without symptoms, it is recommended to seek medical attention in a timely manner, in accordance with the doctor’s instructions for targeted intervention.