Multistate surveillance for laboratory-confirmed, influenza-associated hospitalizations in children: 2003-2004.
BACKGROUND
Increasing use of rapid influenza diagnostics facilitates laboratory confirmation of influenza infections. We describe laboratory-confirmed, influenza-associated hospitalizations in a population representing almost 6% of children in the United States.


METHODS
We conducted population-based surveillance for influenza-associated hospitalizations between October 1, 2003, and March 31, 2004, in 54 counties in 9 states (4.2 million children) participating in the Emerging Infections Program Network. Clinical characteristics, predictors of intensive care unit admission and geographic and age-specific incidence were evaluated.


RESULTS
Surveillance identified 1,308 case-patients; 80% were <5 years and 27% were <6 months of age. Half of the patients and 4 of 5 pediatric deaths did not have a medical indication for influenza vaccination and were outside the 6- to 23-month age group. Twenty-eight percent of case-patients had radiographic evidence of a pulmonary infiltrate, 11% were admitted to intensive care and 3% received mechanical ventilation. The median length of hospital stay was 2 days. Community-acquired invasive bacterial coinfections (1% of patients) were associated with intensive care admission (adjusted odds ratio, 16.9; 95% confidence interval, 5.0-56.8). Thirty-five percent of patients >or=6 months old had received at least one influenza vaccine dose that season. The overall incidence of influenza-associated hospitalizations was 36 per 100,000 children (range per state, 10 per 100,000 to 86 per 100,000).


CONCLUSIONS
Influenza was an important cause of hospitalizations in children during 2003-2004. Hospitalizations were particularly common among children <6 months of age, a group for whom influenza vaccine is not licensed. Continued surveillance for laboratory-confirmed influenza could inform prevention strategies.
Schrag
Stephanie J
SJ
National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. SSchrag@cdc.gov
Shay
David K
DK
Gershman
Ken
K
Thomas
Ann
A
Craig
Allen S
AS
Schaffner
William
W
Harrison
Lee H
LH
Vugia
Duc
D
Clogher
Paula
P
Lynfield
Ruth
R
Farley
Monica
M
Zansky
Shelley
S
Uyeki
Timothy
T
D000293:Adolescent; D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D019411:Clinical Laboratory Techniques; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D007223:Infant; D007251:Influenza, Human / Q000175:diagnosis* / Q000453:epidemiology* / Q000821:virology; D007755:Laboratories, Hospital; D008297:Male; D011159:Population Surveillance; D014481:United States / Q000453:epidemiology