It is often said that fever never goes unnoticed by parents. I think most of us would agree with that and that there seems to be a direct correlation between the level of parental concern and the level of elevation of the mercury.  The question, though, is whether the temperature of 106 degrees F should make us, as health care providers, more concerned.

Hyperpyrexia History

  • In 1976 (that was a good year), McCarthy and Dolan used the term “hyperpyrexia” in relationship to a temperature of 41.1 C (106 F).
  • They found it to be associated with an increased occurrence of serious bacterial infections, particularly meningitis.
  • This, obviously, was prior to the widespread use of vaccinations against HiB and S. pneumoniae.

Hyperpyrexia: What it boils down to…

  • The overall literature is inconclusive.
  • In 1990, Alpert and Fleisher found no correlation between increased risk for serious bacterial infection and hyperpyrexia.
    • State that kids with hyperpyrexia “need to be evaluated as thoroughly and carefully as any other febrile child but do not merit special consideration.”
  • More recently, in 2006, Trautner et al found the following:
    • Out of 130,828 patient visits, 103 had hyperpyrexia.
    • Ages = 3months – 16.9 years.
    • 58% had no identifiable cause!
    • 22 / 103 had laboratory proven viral illness
    • 20 / 103 had serious bacterial infection
      • Bacteremia in 11 of the 20.
      • UTI in 8 of the 20.
    • 17% had an abnormal CXR.
    • Those with underlying medical problems had more risk of serious bacterial infections.
    • Neither age, nor the WBC (once again, it is the last bastion of the intellectually destitute), nor absolute neutrophil count were helpful in risk stratifying patients.
    • Significant limitation: study population was prior to the widespread use of Prevnar vaccine; however, there were only 4 cases of S. pneumoniae.
    • Would seem to indicate that kids with hyperpyrexia are at equal risk of having a Serious Bacterial Infection as they are of having a viral illness… although, again, 58% had no identifiable source.
  • My humble assertion:
    • First of all, nature doesn’t really draw lines in the sand… is there really a difference between 105.8 F and 106 F?
    • The appearance of the child matters more than the number on the thermometer.
    • 106 F does tend to grab providers’ attention and often results in more testing… which is understandable.
    • If the child appears toxic, test everything and start empiric antibiotics! Then think of other stuff to cover (ie, HSV).
    • If the child is not toxic, but has a temperature of 106, it is reasonable to check a blood culture based on the study above.  I would also have a lower threshold for checking U/A, Urine culture and CXR.
    • If you believe the child appears well enough to be treated as an outpatient, I don’t see any utility in checking a WBC, as it will not help you define a source nor will it help you risk stratify your patients with regards to serious bacterial infection.


Trautner BW, Caviness C, Gerlacher GR, et al. Prospective evaluation of the risk of serious bacterial infection in children who present to the emergency department with hyperpyrexia. Pediatrics. 2006; 11: 34 – 40.

Alpert G, Hibbert E, Fleisher GR. Case-control study of hyperpyrexia in children. The Pediatric Infectious Disease Journal. 1990; 9(3)



Sean M. Fox
Sean M. Fox
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