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Approach to the ill-appearing infant (younger than 90 days of age)

Richard J Scarfone, MD, FAAP
Christine Cho, MD, MPH, MEd
Section Editors
George A Woodward, MD
Jan E Drutz, MD
Deputy Editor
James F Wiley, II, MD, MPH


The approach to the ill-appearing infant is reviewed here. The evaluation of fever in infants younger than three months of age is discussed elsewhere. (See "Febrile infant (younger than 90 days of age): Outpatient evaluation" and "Clinical features, evaluation, and diagnosis of sepsis in term and late preterm infants".)


Although infection is the most likely cause of ill appearance among neonates and young infants, a number of other clinical conditions have similar manifestations (table 1).

Infectious causes — Absence of fever does not exclude infection. Young infants with normal or low core temperatures may have serious infections. For example, hypothermia (rectal temperature <36.5°C [97.7°F]) is associated with systemic herpes simplex virus (HSV) infection, and many infants with pertussis are afebrile. (See "Bacterial meningitis in the neonate: Clinical features and diagnosis", section on 'Temperature instability'.)

Bacterial infections

Bacterial sepsis – Infants can develop sepsis from infections such as urinary tract infections (UTIs), bacteremia, meningitis, pneumonia, skin abscess or cellulitis, mastitis, omphalitis, bacterial gastroenteritis, septic arthritis, or osteomyelitis. (See "Febrile infant (younger than 90 days of age): Outpatient evaluation", section on 'Invasive bacterial infection (IBI)'.)

Possible pathogens include the following:

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Literature review current through: Dec 2017. | This topic last updated: Sep 26, 2016.
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