 Although FWS is mostly self-limited and of little clinical concern, the burden on clinicians is to decide which children actually have a serious bacterial infection (SBI) that requires antibiotic treatment and even hospitalization [18,19]. Febrile neonates are at higher risk; the reported incidence of SBI in all febrile neonates presenting to emergency departments varies between 6% and 28% [17,20]. In children, the usual sources/causes of SBI are urinary tract infection, pneumonia, bloodstream infection, and meningitis. With the advent of vaccines for the most common pathogenic serotypes of H. flu and S. pneumonia, the incidence of SBI has dropped significantly [2,3,6,10,13,14]. Although it is implied by the definition of FWS that the etiology of fever is unknown, many studies and guidelines include children with respiratory symptoms [2,3,5,6,8,16,21-24]. For this reason, we were compelled to include in our guidelines for FWS children with respiratory symptoms. Overview of Imaging Modalities A detailed and thorough history and physical examination is the most important component of the diagnostic evaluation of a child with FWS or FUO. Chest radiographs have a role in evaluation of occult pneumonia and should be performed in neonates with FWS and respiratory symptoms and in selected older children with high Reprint requests to: publications@acr.org Discussion of Imaging Modalities by Variant Variants 1 and 2: Neonate younger than 1 month of age with FWS. In febrile neonates younger than 28 days, history and physical examination alone may not be able to completely exclude SBI, even in children who appear clinically well or mildly ill [40]. Therefore, a full sepsis workup is frequently performed. This includes complete blood count, blood culture, urinalysis and urine culture, lumbar puncture with evaluation of cerebrospinal fluid, and administration of antibiotics in the emergency department, followed by hospitalization pending results of cultures [2,3,8,9,22,28].
Fever Without Source or Unknown Origin Child.  Although FWS is mostly self-limited and of little clinical concern, the burden on clinicians is to decide which children actually have a serious bacterial infection (SBI) that requires antibiotic treatment and even hospitalization [18,19]. Febrile neonates are at higher risk; the reported incidence of SBI in all febrile neonates presenting to emergency departments varies between 6% and 28% [17,20]. In children, the usual sources/causes of SBI are urinary tract infection, pneumonia, bloodstream infection, and meningitis. With the advent of vaccines for the most common pathogenic serotypes of H. flu and S. pneumonia, the incidence of SBI has dropped significantly [2,3,6,10,13,14]. Although it is implied by the definition of FWS that the etiology of fever is unknown, many studies and guidelines include children with respiratory symptoms [2,3,5,6,8,16,21-24]. For this reason, we were compelled to include in our guidelines for FWS children with respiratory symptoms. Overview of Imaging Modalities A detailed and thorough history and physical examination is the most important component of the diagnostic evaluation of a child with FWS or FUO. Chest radiographs have a role in evaluation of occult pneumonia and should be performed in neonates with FWS and respiratory symptoms and in selected older children with high Reprint requests to: publications@acr.org Discussion of Imaging Modalities by Variant Variants 1 and 2: Neonate younger than 1 month of age with FWS. In febrile neonates younger than 28 days, history and physical examination alone may not be able to completely exclude SBI, even in children who appear clinically well or mildly ill [40]. Therefore, a full sepsis workup is frequently performed. This includes complete blood count, blood culture, urinalysis and urine culture, lumbar puncture with evaluation of cerebrospinal fluid, and administration of antibiotics in the emergency department, followed by hospitalization pending results of cultures [2,3,8,9,22,28].