Infants with high fever of 39 degrees can be seen in intracranial infections, toddler rash, urinary tract infections and other diseases, whether the risk of combining the baby’s condition to determine the comprehensive, the duration is not the only factor to determine, it is recommended to consult a doctor in a timely manner. 1. Intracranial infections: such as bacterial meningitis, viral encephalitis, clinical high fever, accompanied by convulsions and depression and other phenomena, the seriousness of the condition can occur repeatedly elevated temperature, the use of antipyretic drugs ineffective, frequent convulsions and lethargy, etc., need to be actively consult a specialist physician to determine whether it is dangerous to judge the duration of the high fever alone. 2. Early childhood emergency rash: caused by human herpesvirus infection, high fever can occur during the course of the disease, some babies may also appear temperature rises repeatedly, the use of antipyretic drugs ineffective, but after active treatment of the disease has a good prognosis, the rash appeared after 3~5 days of fever, the body temperature gradually normalized. 3. Urinary tract infections: the acute phase of the disease can occur repeatedly elevated body temperature, active formal treatment of body temperature can gradually return to normal. If the baby’s spirit is poor, repeated fever lasts a long time, it is necessary to improve the relevant auxiliary tests such as blood culture, urine culture, etc., can not be assessed only by the duration of high fever. 4. Other: such as acute leukemia, the course of the disease can appear fever, fever type is not certain, can be manifested as low or high fever, such diseases are more dangerous, need to take chemotherapy, symptomatic and other integrated treatment. Infants with a high fever of 39 degrees is recommended to actively seek medical attention, by the specialist physician comprehensive assessment and judgment.