Viral fever in children takes several days, mainly related to the specific cause, fever type and the individual situation of the child, can not be generalized. If the rash is caused by herpes simplex virus, the fever usually subsides after 3-4 days, and the fever duration is more certain. In the case of measles caused by the measles virus, the rash usually appears when the fever is 5 days old, but the fever is higher during the rash period, after which the fever continues for 3-4 days and then begins to subside, with a relatively long fever duration. In addition, if the fever is caused by influenza virus, the duration is longer. In this case, infectious fever caused by influenza A virus will last for about 7 days. There may also be recurrent high fever and the disease progresses relatively quickly. The exact duration varies from person to person. If a child has a fever accompanied by poor mental health and difficulty in breathing, parents are advised to take the child to the pediatric internal medicine department of the hospital for examination and treatment in a timely manner.