Burden of seasonal influenza hospitalization in children, United States, 2003 to 2008.
OBJECTIVE
To estimate the rates of hospitalization with seasonal influenza in children aged <18 years from a large, diverse surveillance area during 2003 to 2008.


METHODS
Through the Emerging Infections Program Network, population-based surveillance for laboratory-confirmed influenza was conducted in 10 states, including 5.3 million children. Hospitalized children were identified retrospectively; clinicians made influenza testing decisions. Data collected from the hospital record included demographics, medical history, and clinical course. Incidence rates were calculated with census data.


RESULTS
The highest hospitalization rates occurred in children aged <6 months (seasonal range, 9-30/10 000 children), and the lowest rates occurred in children aged 5 to 17 years (0.3-0.8/10 000). Overall, 4015 children were hospitalized, 58% of whom were identified with rapid diagnostic tests alone. Forty percent of the children who were hospitalized had underlying medical conditions; asthma (18%), prematurity (15% of children aged <2 years), and developmental delay (7%) were the most common. Severe outcomes included intensive care unit admission (12%), respiratory failure (5%), bacterial coinfection (2%), and death (0.5%).


CONCLUSIONS
Influenza-associated hospitalization rates varied by season and age and likely underestimate true rates because many hospitalized children are not tested for influenza. The proportion of children with severe outcomes was substantial across seasons. Quantifying incidence of influenza hospitalization and severe outcomes is critical to defining disease burden.
Dawood
Fatimah S
FS
Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. fdawood@cdc.gov
Fiore
Anthony
A
Kamimoto
Laurie
L
Bramley
Anna
A
Reingold
Arthur
A
Gershman
Ken
K
Meek
James
J
Hadler
James
J
Arnold
Kathryn E
KE
Ryan
Patricia
P
Lynfield
Ruth
R
Morin
Craig
C
Mueller
Mark
M
Baumbach
Joan
J
Zansky
Shelley
S
Bennett
Nancy M
NM
Thomas
Ann
A
Schaffner
William
W
Kirschke
David
D
Finelli
Lyn
L
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D007251:Influenza, Human / Q000453:epidemiology* / Q000628:therapy; D008297:Male; D012189:Retrospective Studies; D012621:Seasons; D013997:Time Factors; D014481:United States / Q000453:epidemiology