The evaluation of neonates and young infants younger than three months with fever is discussed below. The definition and etiology of fever in this age group, as well as traditional strategies for evaluating young infants with fever, are discussed separately. (See "Definition and etiology of fever in neonates and infants (less than three months of age)" and "Strategies for the evaluation of fever in neonates and infants (less than three months of age)".)
In addition, the diagnosis and treatment of specific infections, including meningitis, pneumonia, and urinary tract infections and the evaluation of infants and children 3 to 36 months of age are discussed elsewhere. (See "Bacterial meningitis in children older than one month: Clinical features and diagnosis" and "Community-acquired pneumonia in children: Clinical features and diagnosis" and "Urinary tract infections in newborns" and "Fever without a source in children 3 to 36 months of age".)
Although most neonates (younger than 28 days of age) and young infants (29 to 90 days of age) with fever have a benign viral illness, the goal of the evaluation is to identify those children who are at high risk for serious bacterial illness (eg, bacteremia, urinary tract infection, meningitis, bacterial gastroenteritis, or pneumonia), and who therefore require empiric antimicrobial therapy and possibly hospitalization.
The young febrile infant may demonstrate few, if any, interpretable clues to the underlying illness . The limitations of the history and physical examination in neonates and young infants with fever traditionally have led to an aggressive laboratory evaluation, even for patients who were previously healthy, are well-appearing, and have no focal infection. In the past, most of these patients have been admitted to the hospital for antibiotic treatment pending negative cultures. This practice is expensive and can result in iatrogenic morbidity for a substantial number of infants . Subsequently, criteria have been developed that can identify young infants with fever who are at low risk for serious bacterial illness and can be safely managed as outpatients (algorithm 1). (See "Strategies for the evaluation of fever in neonates and infants (less than three months of age)", section on 'Traditional strategies'.)
A thorough history is an essential component of the evaluation of all neonates and young infants with fever (T ≥38ºC or 100.4°F). The history should address the following clues to the etiology of the fever: