Febrile Infant

A fever in a young infant is not managed like a fever in a toddler. A temperature of 38.0°C (100.4°F) or higher is the threshold that triggers evaluation in infants 8–60 days old. This includes a qualifying fever documented rectally in the clinical setting or reported at home within the preceding 24 hours. The reason is physiologic vulnerability. Young infants can have invasive infection with few localizing findings; they may not cough, point to pain, or develop an obvious source. A baby who looks comfortable at first can deteriorate quickly as infection impairs perfusion, glucose regulation, breathing, and temperature control. Age in days matters. The risk of invasive bacterial infection falls as infants mature, so the same temperature produces a different plan at 14 days than at 45 days. Do not use the height of fever, a temporary response to acetaminophen, or a negative maternal group B streptococcus screen to decide that an infant is low risk.