Question

A $14$-day-old male infant is brought to the pediatric emergency department by his parents due to a fever noted at home. The parents report that he has been feeding slightly less than usual over the past $24$ hours but is producing a normal number of wet diapers. He was born at $38$ weeks gestation via uncomplicated spontaneous vaginal delivery. Maternal group B *Streptococcus* screening was negative. The mother reports no history of genital ulcers, although she does have a history of occasional oral cold sores. On physical examination, the infant is awake and alert. Vital signs show a temperature of $38.8^\circ\text{C}$ ($101.8^\circ\text{F}$), heart rate of $160/\text{min}$, and respiratory rate of $42/\text{min}$. Skin examination reveals a cluster of $4$ small, erythematous vesicles on the right shoulder. The anterior fontanelle is flat, and the neurological examination is nonfocal. Laboratory studies show a peripheral leukocyte count of $12,500/\mu\text{L}$. Urinalysis is unremarkable. Which of the following is the most appropriate next step in management?