The history and physical assessments of the febrile infant.

Grading patient clinical appearance using the Young Infant Observation Scale and the Yale Observation Scale can effectively classify approximately 75% of infants with a serious illness or infection as ill appearing and 95% who appear to be well as having low risk for serious illness or infection. Most children with invasive bacterial infections appear to be ill at the time of evaluation, although exceptions to this are not uncommon. Accuracy in distinguishing the etiology of fever in infants is an integrated evaluation including thorough assessment of historical data, clinical appearance, and physical findings.