A 9-month-old baby with a fever of 39°C should first use antipyretic medication, commonly used drugs include Mennen, etc. Physical cooling can be given, such as warm water baths or antipyretic patches, while actively seeking medical attention to improve blood tests, C-reactive protein and other related tests. Common pathogens include viruses, bacteria, or atypical pathogens, with viruses being the most common. If the patient is infected with a virus, oral oseltamivir, Abidor and other related drugs can be administered for treatment. When the patient is diagnosed with a bacterial infection, treatment with antibiotics, such as cefixime, amoxicillin, azithromycin, etc., or intravenous antibiotics may be given if necessary, is required. If the patient is infected with mycoplasma, macrolides such as azithromycin and erythromycin are needed.