Sudden fever in babies without symptoms may be related to colds, gastrointestinal diseases, central nervous system infections and so on. 1. Colds: some babies with colds will first have a fever, and in the following 2-3 days may have runny nose, sore throat, cough and other manifestations, parents need to continue to observe the baby’s condition. 2. Gastrointestinal diseases: some babies with gastroenteritis will first show fever, and later nausea, vomiting, abdominal distension, diarrhea. 3. central nervous system infections: some babies first appear fever, and later appear projectile vomiting, convulsions and so on. There are many other reasons for babies to have asymptomatic sudden fevers, so parents are advised to take their babies to the hospital for a comprehensive examination and receive regular treatment as soon as possible.