II. Definition

  1. Age under 36 months old
    1. Highest risk in younger infants (especially <29 days) and unimmunized
  2. Significant Fever (based on Rectal Temperature)
    1. Age <90 days: >38 C (100.4 F)
    2. Age >90 days and unimmunized: >39 C (102.2 F) - 3% Occult Bacteremia risk
    3. Age >90 days and immunized: No defined Temperature cutoff (lower risk)
  3. No localizing signs
    1. Acute onset of fever persisting <1 week
    2. Findings dictating assessment for Occult Bacteremia or serious Bacterial illness

III. Epidemiology

  1. Well appearing, term infants age <60 days with fever (>38 C or 100.4 F)
    1. Bacteremia Prevalence 1.8% (up to 3.1% if under age 28 days)
    2. E. coli (39.3%) and Group B Streptococcus (24%) were most common
    3. Bacteremia was accompanied by Urinary Tract Infection in 43%, and by Meningitis in 13%
    4. Meningitis primarily occured in infants <28 days, with a 0.2% rate in those 29 to 60 days old
    5. Powell (2017) Ann Emerg Med +PMID: 28988964 [PubMed]

IV. Precautions

  1. Decision rules in Occult Bacteremia assume an otherwise well child
    1. Sepsis evaluation is required in a toxic appearing child regardless of decision criteria
    2. Children with chronic disease risk factors (see below) also require Sepsis evaluation
  2. Bacteremia occurs in even well appearing infants (<60-90 days), despite reassuring decision rule results
    1. See epidemiology above
    2. Exercise caution in age <90 days (esp. <28 days)
    3. Most infants <28 days undergo full workup (including Lumbar Puncture) and are admitted
    4. Urinalysis abnormalities do not exclude other source
    5. Mason, Claudius and Behar in Herbert (2018) EM:Rap 18(2): 6-7

V. Causes: Common etiologies of Occult Bacteremia

  1. Newborns and age 1-3 months
    1. Urinary Tract Infections are the most common cause of serious Bacterial Infections in this age group
    2. Group B Beta-hemolytic Streptococcus (Group B Strep)
    3. Escherichia coli K1 (ECK1)
    4. Klebsiella species
    5. Listeria monocytogenes
      1. Rare in the United States
      2. Predominant in Spain
    6. Neonatal Herpes Simplex Virus (HSV)
      1. Incidence similar to Bacterial Meningitis (25 to 50 cases per 100,000 live births in U.S.)
  2. Children 3-36 months
    1. Pneumonia and Urinary Tract Infections
      1. Most common cause of serious Bacterial Infections in this age group
    2. Most common prior to Prevnar (PCV7) and Hib Vaccines (down to <0.2% Incidence)
      1. Streptococcus Pneumoniae
        1. Accounted for 80-90% of Occult Bacteremia pre-PrevnarVaccine (PCV7)
      2. HaemophilusInfluenzae
        1. Prior to Hib Vaccine
          1. Most common cause of Meningitis and invasive disease <5 years old
        2. Since Hib Vaccine
          1. Incidence of Hib-related serious Bacterial Infections has dropped 99%
    3. Other causes of serious Bacterial illness in ages 3-36 months
      1. Group A Beta-hemolytic Streptococcus
      2. Neisseria Meningitidis

VI. Associated Conditions: Occult Bacteremia underlying causes

VII. Risk Factors: High risk conditions for Occult Bacteremia regardless of patient appearance

  1. Serious underlying chronic diseases
    1. Immunosuppression
    2. Sickle Cell Disease
    3. Asplenia
    4. Congenital Heart Disease
    5. Ventriculoperitoneal Shunt
  2. Assumes no regular medical interventions
    1. Hemodialysis
    2. Ongoing intravenous therapy
    3. Indwelling catheter

VIII. Signs

  1. See Toxic Findings Suggestive of Occult Bacteremia
  2. Fever height no longer correlates with seriousness of illness
    1. Pneumococcus and H. Influenzae were asscociated with fevers over 105 F prior to Prevnar and Hib Vaccines
    2. Fever to 105 or 106 F should now be approached the same as lower Temperature spike without focus

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