Among young infants presenting with fever, untreated serious bacterial infections can have severe outcomes, so a full sepsis workup is often recommended but may not be necessary. This issue reviews the use of novel diagnostic tools such as procalcitonin, C-reactive protein, and RNA biosignatures as well as new risk stratification tools such as the Step-by-Step approach and the Pediatric Emergency Care Applied Research Network prediction rule to determine which febrile young infants require a full sepsis workup and to guide the management of these patients in the emergency department. The most recent literature assessing the risk of concomitant bacterial meningitis with urinary tract infections and the role for viral testing, specifically herpes simplex virus and enterovirus, are also reviewed.