Evaluating Fever of Unidentifiable Source
in Young Children
DENISE K. SUR, MD, and ELISE L. BUKONT, DO, University of California, Los Angeles, Los Angeles, California
E
ven with a thorough history and
a complete physical examina-
tion, one in five acutely ill, non-
toxic-appearing children have an
unidentifiable source of fever.1-4 Although
most of these children have a self-limited
viral illness, studies from the 1980s and
1990s have shown that 7 to 13 percent of
children younger than 36 months without
evident sources of fever had occult bactere-
mia and serious bacterial infection (SBI).5-7
More recent research has demonstrated
a significant decrease in the number of
cases of occult bacteremia and SBI in febrile
children since the advent of Haemophilus
influenzae type b and Streptococcus pneu-
moniae vaccines, with occult bacteremia
rates of 1.6 to 1.8 percent.3,8 Epidemiologic
data also have shown a decrease in the
rates of S. pneumoniae infections since the
introduction of a pneumococcal conjugate
vaccine.9-13 Although recommendations may
change, physicians should still take a cau-
tious approach because of the potential for
adverse consequences from unrecognized
and untreated SBI.
Definitions of Fever and SBI
A clinically significant fever is generally
defined as a rectal temperature of 100.4° F
(38° C) or higher. For previously healthy,
well-appearing children three to 36 months of
age, a temperature of 102.2° F (39° C) requires
further evaluation.6,14,15 Studies of children
with fever with no clear source consistently
defined fever using rectal temperature. A
number of studies have shown that axillary
and tympanic temperatures are unreliable in
young children.16-22 A child with a history of a
rectal temperature higher than 100.4° F who is
afebrile at the time of presentation should be
given the same level of attention as one who
has a fever at presentation.9,23-26
In the studies cited in this article, the SBIs
found included bacteremia, bacterial gastro-
enteritis,