The clinical characteristics and infectious outcomes of febrile infants aged 8 to 12 weeks.

We reviewed 356 consecutive cases of febrile infants aged 8 to 12 weeks who received outpatient evaluation for sepsis over 4 years. Thirty-three infants (9.3%) had a serious bacterial infection (SBI), including bacterial meningitis, bacteremia, urinary tract infection (UTI), and Salmonella enteritis. The SBI rate, which was directly proportional to fever height, was significantly greater for infants with hyperpyrexia (35%) than those with lesser degrees of fever (7.7%) and for infants with peripheral blood leukocytosis (total WBC count > or = 15,000/mm3; 25%) than those with lesser total WBC counts (5.8%). An attending-level physician judged that 67% of infants with SBI appeared to be "well," including five or eight cases (63%) of bacteremia, 14 of 17 cases (82%) of UTI, and all three cases of Salmonella enteritis, whereas all five patients with bacterial meningitis appeared to be "ill." Urinalysis abnormalities indicative of UTI were present in 15 of 17 infants (88%) who had this infection. SBIs are not uncommon in febrile infants aged 8 to 12 weeks and occur significantly more often in those with either hyperpyrexia or peripheral blood leukocytosis.