Fever is a prominent symptom of many different disease processes. Neonates and young infants may manifest fever as the only sign of significant underlying infection. Clinically distinguishing those with a serious febrile illness from those who are mildly ill may be difficult . This has led to an aggressive approach to fever in this age group, usually including diagnostic tests, empiric antibiotics and, often, hospital admission.
A systematic approach to evaluating infants with fever without a source in this age group would ideally identify the patient with a serious bacterial illness (SBI) and minimize the testing and treatment of the patient with a mild illness. Several strategies for identifying the infant with fever who has an SBI have been proposed and tested. The strengths and limitations of these protocols, as well as the utilization of proposed guidelines are discussed here.
The definition, immunologic vulnerability, and etiology of fever in infants less than three months of age, as well as the evaluation and management of fever in these patients, are discussed elsewhere. (See "Definition and etiology of fever in neonates and infants (less than three months of age)" and "Evaluation and management of fever in the neonate and young infant (younger than three months of age)".)
Several studies have attempted to identify patients who can be managed safely as outpatients with or without empiric antibiotic treatment . There is some variation among them regarding inclusion criteria, inpatient or outpatient population, and whether or not antibiotics were given expectantly. This has led to confusion in the literature and a lack of consensus regarding the optimal approach to young infants with fever. Furthermore, even when guidelines have been proposed, they have not been consistently followed by many practitioners in the community [3-5]. (See 'Problems with these approaches' below.)
Nevertheless, these studies established the safety of treating a select population of young infants as outpatients. The sum of these studies suggests that the incidence of serious bacterial infection (SBI) among infants categorized as low risk after a full evaluation is 2.2 percent (range, 0 to 6.3 percent) . When limited to studies that prospectively identified infants at low risk of SBI (algorithm 1) and performed outpatient observation with no antibiotics, the frequency of SBI varied from 0.5 to 1.1 percent in studies that either did or did not include lumbar puncture as part of the initial evaluation, respectively . (See "Evaluation and management of fever in the neonate and young infant (younger than three months of age)", section on 'Evaluation and management'.)