Influenza virus infection and the risk of serious bacterial infections in young febrile infants.

Objective: We aimed to determine the risk of SBIs in febrile infants with influenza virus infections and compare this risk with that of febrile infants without influenza infections.

Patients And Methods: We conducted a multicenter, prospective, cross-sectional study during 3 consecutive influenza seasons. All febrile infants or=5 x 10(4) colony-forming units per mL or >or=10(4) colony-forming units per mL in association with a positive urinalysis. Bacteremia, bacterial meningitis, and bacterial enteritis were defined by growth of a known bacterial pathogen. SBI was defined as any of the 4 above-mentioned bacterial infections.

Results: During the 3-year study period, 1091 infants were enrolled. A total of 844 (77.4%) infants were tested for the influenza virus, of whom 123 (14.3%) tested positive. SBI status was determined in 809 (95.9%) of the 844 infants. Overall, 95 (11.7%) of the 809 infants tested for influenza virus had an SBI. Infants with influenza infections had a significantly lower prevalence of SBI (2.5%) and UTI (2.4%) when compared with infants who tested negative for the influenza virus. Although there were no cases of bacteremia, meningitis, or enteritis in the influenza-positive group, the differences between the 2 groups for these individual infections were not statistically significant.

Conclusions: Febrile infants