Risk of Serious Bacterial Infection in Infants Aged ≤60 Days Presenting to Emergency Departments with a History of Fever Only

Objective: To compare the risk of serious bacterial infection between infants aged ≤60 days who are febrile in the emergency department (ED) and those who have only a history of fever and are afebrile on arrival to the ED. Study design: In this secondary analysis of a multicenter prospective study using data collected between December 2008 and May 2013, we compared the rate of serious bacterial infection (urinary tract infection [UTI], bacteremia, and/or bacterial meningitis) between infants who have a history of fever but are afebrile on arrival to the ED and those with fever documented in the ED (rectal temperature ≥38.0 °C) using relative risk (RR) with 95% CI. Stratified analyses were performed for age (≤28 and 29-60 days) and serious bacterial infection type. Infants born prematurely and those with a clinical focal infection or serious illness were excluded. Results: A total of 3825 infants (mean age, 35.2 days; 56.9% male) were included. Of the 1233 (32.2%) who were afebrile in the ED, 108 (8.8%) had a serious bacterial infection (UTI, n = 94 [7.6%]; bacteremia, n = 19 [1.5%]; bacterial meningitis, n = 8 [0.6%]). Of the 2592 infants (67.8%) who were febrile in the ED, 331 (12.8%) had a serious bacterial infection (UTI, n = 285 [11.0%]; bacteremia, n = 61 [2.4%]; bacterial meningitis, n = 17 [0.7%]). The RR for serious bacterial infection for afebrile vs febrile infants was 0.68 (95% CI, 0.56-0.84). A lower risk of serious bacterial infection was also seen among afebrile vs febrile infants aged ≤28 days (RR, 0.69; 95% CI, 0.52-0.93) and age 29-60 days (RR, 0.67; 95% CI, 0.50-0.89). Conclusions: The prevalence of serious bacterial infection is lower in infants aged ≤60 days with a history of fever compared with those who are febrile on arrival to the ED. The small risk reduction in this group is unlikely to alter decision making.