• Fever: ≥ 38 oC measured rectally (oral are 0.6 oC lower than rectal and axillary are 0.6 oC lower than oral
  • Fever of unknown origin: daily rectal temperature >38.3oC lasting >2weeks (cause not determined through history, physical, diagnostics)
  • Heatstroke: temperature >42oC with anhydrosis and coma (80% mortality)


  1. Raised hypothalamic set point (infection, collagen vascular disease, malignancy) –> antipyretics are helpful
  2. Excess heat production (salicylate overdose, hyperthyroid, environmental heat, malignant hyperthermia)
  3. Defective heat loss (ectodermal dysplasia, heat stroke, anticholinergic overdose)

Differential Diagnosis

  • Infection:
    • Viral vs bacterial
    • 0-3months: UTI is most common bacterial infection (E. coli, enterococcus)
    • Bacteriemia, meningitis (N meningitides if petechiae)
    • HSV (neurologic findings)
    • Appendix, AOM (S. pneumo, H influenzae), gastroenteritis, strep pharyngitis, bronchiolitis, pneumonia (S. pneumo, Mycoplasma pneumo, H. flu, GBS, RESV, Influenza, Parainfluenza, Adenovirus, Coxsackie)
    • Cardiac abnormality – think endocarditis
  • Inflammatory
    • Kawasaki (5 days of high fever, truncal/polymorphous rash, bilateral nonpurulent conjunctivitis, changes in oral mucosa specifically lips and tongue, desquamation, cervical lymphadenopathy)
    • Inflammatory bowel disease
    • Juvenile rheumatoid arthritis
  • Drugs/Toxins
  • Neoplasm
    • Acute lymphocytic leukemia (ALL)
    • Lymphoma

Fevers that kill…

0-2 months

2-36 months

36+ months











Bacterial tracheitis




Acute Lymphocytic Leukemia









  • Clarify: onset, duration, how measured, height
    • Up until the age of 5 the rectal route is gold standard.  Oral may be used in toddlers but thermometer should be held under tongue for ~4 minutes.  The TM route is becoming more favourable.  Axillary method should not be used.
  • General symptoms: playful, listless, malaise, lethargy
  • Systems: CNS, Resp, GI, GU, MSK, Derm
  • Obstetrics: GBS status, premature rupture of membranes (PROM), premature
  • Season:
    • Winter – influenza, RSV
    • Spring/Autumn – parainfluenza
    • Summer – enterovirus
  • Immunizations: encapsulated (S. pneumo, N. meningitides, HiB)
  • Travel
  • Animal exposure

Physical exam

  • ABCs, vitals
  • Assess hydration status
  • Full physical (including CNS)

Rochester Criteria

  • According to eMedicine:
    • Rate of bacteremia
      • Febrile infants younger than 2 months: 2-3%
      • First month of life: 7-8%
      • Infants aged 3-24 months: 3.5-4%
      • Nontoxic infants aged 0-60 days (SBI): 4-16%.
  • Useful for identifying febrile infants (<90days of age) who are at a low risk of having a serious bacterial infection
    • Infants must be previously healthy and have no history of antibiotics
    • No evidence of ear, soft tissue or skeletal infection
    • WBC between 5000 and 15000/mm3
    • Bands <1500/mm3
    • U/A with <10WBC/hpf
    • If diarrhea, stool < 25WBC/hpf


  • Full septic workup:
    • CBC+D
    • Blood culture
    • Urinalysis
    • Urine culture
    • Lumber puncture (LP) (especially < 2months but for exam say if less than 1 yr ALWAYS)
    • +/- Chest x-ray
    • Swabs (NP, throat, rectal)
    • ESR
    • Stool for C+S and O+P

Full septic workup  for kiddies under 1 yr with lethargy and non specific symptoms (including LP)


  • Treatment…
    • If at increased risk from complications
    • If increased metabolic demands because at risk for decompensation
    • If uncomfortable
  • Tylenol 10-15mg/kg q4-6h
  • Ibuprofen 5-10mg/kg q6-8h
  • No ASA (Reye’s syndrome – post URTI/Varicella – vomiting, CNS changes, liver enlargement)
  • Antibiotics (empiric antibiotics if suspected meningitis – continue until culture results back!)
    • Up to 3 months
      • Listeria, E. coli, GBS, pneumococcus, meningococcus, H. flu
        • Amp/Gent in month 1 (synergistic)
        • Amp + Cefotaxime/Ceftriaxone (good BBB penetration) in month 2-3
    • 3 months to 3 years
      • May have occult bacteremia
      • Teething can cause low grade fever
      • Full septic workup minus LP (unless risks)

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