Influenza B virus usually causes a mild and self-limiting illness. A 2-month-old infant presented with acute symptoms suggestive of septic shock but recovered after vigorous resuscitation 1 day later. Influenza B was isolated from a throat swab taken from the infant. Bacterial cultures of blood, urine and spinal fluid had no growth. This case illustrates that the clinical signs and symptoms of influenza in infants may be indistinguishable from bacterial sepsis.