What causes a sudden fever of 38.5°C in a child?

　　A sudden fever of 38.5°C in a child may be caused by viral infection, bacterial infection, or mycoplasma infection, among other reasons.

　　1. Viral infection

　　A sudden fever of 38.5°C in a child may result from a viral infection. Under a physician’s guidance, antiviral medications such as ribavirin granules or oseltamivir phosphate granules may be administered orally. Additionally, antipyretics—including acetaminophen tablets or ibuprofen granules—should be used concurrently to manage fever.

　　2. Bacterial infection

　　If the fever is due to bacterial infection, anti-infective therapy under medical supervision is required, using agents such as cefaclor dry suspension or azithromycin granules. Antipyretics—such as acetaminophen tablets or ibuprofen suspension—should also be administered alongside antimicrobial treatment to support recovery.

　　3. Mycoplasma infection

　　Fever caused by mycoplasma infection requires not only the aforementioned antipyretics but also combination therapy with macrolide antibiotics—such as azithromycin dry suspension or spiramycin granules—to effectively reduce fever.