PEDIATRICS Vol. 108 No. 4 October 2001, p. e63
Received Sep 19, 2001; accepted May 17, 2001.

From the Departments of * Pediatrics and Objectives. To compare the incidence
of febrile seizures in children hospitalized for influenza A infection
with parainfluenza and adenovirus infection and to examine the
hypothesis that children hospitalized for influenza A (variant
Sydney/H3N2) during the 1998 season in Hong Kong had more frequent and
refractory seizures when compared with other respiratory viruses,
including the A/Wuhan H3N2 variant that was present in the previous
year.
Methods. Medical records of children between 6 months and
5 years of age admitted for influenza A infection in 1998 were
reviewed. For comparison, records of children of the same age group
with influenza A infection in 1997, and with parainfluenza and
adenovirus infections between 1996 and 1998 were reviewed. Children who
were afebrile or who had an underlying neurologic disorder were
excluded.
Results. Of children hospitalized for influenza A in 1998 and 1997, 54/272 (19.9%) and 27/144 (18.8%) had febrile seizures,
respectively. The overall incidence of febrile seizures associated with
influenza A (19.5%) was higher than that in children hospitalized for
parainfluenza (18/148; 12.2%) and adenovirus (18/199; 9%) infection,
respectively. In children who had febrile seizures, repeated seizures
were more commonly associated with influenza A infection than with
parainfluenza or adenovirus infection (23/81 [28%] vs 3/36
[8.3%], odds ratio [OR] 4.3, 95% confidence interval: 1.2 to
15.4). Alternatively, children with influenza A infection had a higher
incidence (23/416, 5.5%) of multiple seizures during the same illness
than those with adenovirus or parainfluenza infection (3/347, 0.86%;
OR 6.7, 95% confidence interval: 2.0-22.5.) The increased incidence
of febrile seizures associated with influenza A was not attributable to
differences in age, gender, or family history of febrile seizure. Multivariate analysis, adjusted for peak temperature and duration of
fever, showed that hospitalized children infected with infection A had
a higher risk of febrile seizures than those who were infected with
parainfluenza or adenovirus (OR 1.97). Influenza A infection was a significant cause of febrile seizure
admissions. Of 250 and 249 children admitted to Queen Mary Hospital for
febrile seizures in 1997 and 1998, respectively, influenza A infection
accounted for 27 (10.8%) admissions in 1997 and 54 (21.7%) in 1998. During months of peak influenza activity, it accounted for up to 35%
to 44% of febrile seizure admissions. In contrast, parainfluenza,
adenovirus, respiratory syncytial virus, and influenza B had a smaller
contribution to hospitalizations for febrile seizures, together
accounting for only 25/250 (10%) admissions in 1997 and 16/249 (6.4%)
in 1998.
Conclusion. The influenza A Sydney variant (H3N2) was not
associated with an increased risk of febrile seizures when compared
with the previous influenza A Wuhan variant (H3N2) or H1N1 viruses.
However, in hospitalized children, influenza A is associated with a
higher incidence of febrile seizures and of repeated seizures in the same febrile episode than are adenovirus or parainfluenza infections. The pathogenesis of these observations warrants additional studies. Complex febrile seizures, particularly multiple febrile seizures at the
time of presentation, have been thought to carry an adverse long-term
prognosis because of its association with a higher incidence of
epilepsy. Repeated febrile seizures alone, particularly if associated
with influenza A infection, may not be as worrisome as children with
complex febrile seizures because of other causes, which requires
additional investigation. This may subsequently have an impact on
reducing the burden of evaluation in a subset of children with complex
febrile seizures.
Microbiology,
University of Hong Kong, Hong Kong SAR, China.
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