A 6-year-old girl from Mumbai is brought to the pediatric ward with a 3-day history of fever, headache, vomiting, and irritability. On examination, she is drowsy but arousable, with neck stiffness and a positive Kernig sign. Temperature is 38.5°C. Lumbar puncture is performed: CSF is clear, WBC 85/μL (predominantly lymphocytes), protein 65 mg/dL, glucose 48 mg/dL (serum glucose 92 mg/dL), Gram stain is negative, bacterial culture is negative. Blood culture is also negative. PCR for enterovirus from CSF is positive. What is the most appropriate management?