Fever Without Source in Unvaccinated Children Aged 3 to 24 Months: What Workup Is Recommended?

Fever is the most common complaint for infants and children brought to the emergency department. Most febrile children younger than 3 years will have a clinically apparent source of infection. However, in approximately 20% of these children, a source cannot be identified by history and physical examination alone. The recommended diagnostic approach to children younger than 3 years presenting with fever without source (FWS) has changed dramatically over the past 30 years because of the widespread use of the Haemophilus influenza type b and polyvalent pneumococcal vaccines. The percentage of children in the United States unvaccinated at 24 months is now over 1% and seems to be increasing. This article will review what is currently known about FWS in children aged 3 to 24 months in the modern era and how it pertains to unvaccinated children treated in the emergency department. An algorithm for the treatment of unvaccinated young children presenting with FWS is proposed.