Heart Rate Variability in Febrile Young Infants

Febrile infants younger than 3 months old present a diagnostic dilemma to the emergency physician. Tension remains between the need for early aggressive intervention among patients with suspected sepsis and the global phenomena of increasing antibiotic resistance. The investigators aim to: (1) To study the association between heart rate variability (HRV) and the presence of a serious infection (SI) among infants younger than 3 months old. The investigators hypothesize that a reduced HRV is associated with the presence of SI. (2) To compare HRV between febrile infants \< 3 months with non-febrile infants. The investigators hypothesize that the variability will be reduced in febrile infants with SIs when compared to non-febrile well infants, but not among febrile infants without SIs when compared to non-febrile well infants. (3) To study if HRV will provide incremental diagnostic information over current triage tools.