Children’s viral infections can be seen in acute upper respiratory tract infections, bronchopneumonia or infectious mononucleosis and other conditions, the duration of high fever needs to be combined with the specifics of the infection and their own constitution to make a comprehensive judgment, such as acute upper respiratory tract infections usually need about 3 to 7 days to recover. 1. Acute upper respiratory tract infection: mostly caused by viruses (such as rhinovirus, respiratory syncytial virus) infection, clinical fever, body temperature can be as high as 39 ~ 40 ℃, fever in 2 ~ 3 days to about 1 week. 2. Bronchopneumonia: such as adenovirus pneumonia, caused by adenovirus infection, such children are more acute onset of symptoms of toxicity, high fever lasts a long time, the temperature can be up to 39 ℃ or more, was arrested fever or chiropractic fever, fever, which can last for 2 ~ 3 weeks, in addition to fever symptoms, accompanied by a significant cough, dysphoria, severe respiratory distress, seizures, etc.. 3. Infectious mononucleosis: it is an acute infectious disease caused by EBV, mainly affecting children and adolescents, clinical symptoms can be sore throat, liver and spleen lymph node enlargement and fever symptoms, fever temperature of 38~40 ℃, no fixed fever, most of the fever 1~2 weeks, a few up to several months. 4. Other: such as toddler emergency rash, is caused by human herpes virus infection, such babies more high fever for 3~5 days, heat out of the rash. It is recommended to consult a specialist for evaluation and judgment.