Influenza-associated cystic fibrosis pulmonary exacerbations.
BACKGROUND
Although cystic fibrosis (CF) is the most common inherited respiratory disease, the burden of influenza among individuals with CF is not well characterized.


METHODS
We used the CF Foundation Patient Registry to determine the relationship between pulmonary exacerbation incidence rate and influenza virus season from July 2003 through June 2007. The outcome of interest, pulmonary exacerbation, was defined as treatment of a respiratory illness with IV antibiotics. Each influenza season was defined as all months during which >/= 15% of laboratory tests for influenza virus were positive in the US influenza virologic surveillance system. We calculated incidence rates of pulmonary exacerbation during the influenza and summertime seasons as well as relative rates with 95% CIs. A multivariate regression model adjusted for demographic and clinical predictors.


RESULTS
In 2003, the patient cohort size was 21,506 patients, and 7,727 patients experienced at least one pulmonary exacerbation. The overall pulmonary exacerbation incidence rate in the influenza season was 595.0 per 10,000 person-months compared with a summertime baseline of 549.6 per 10,000 person-months. The incidence rate ratio was 1.08 (95% CI: 1.06, 1.10). Multivariate analysis did not change our estimate of risk (adjusted odds ratio: 1.07; 95% CI: 1.05, 1.10). An estimated annual excess of 147.6 per 10,000 person-months or an excess 2.1% of total exacerbations occur during the influenza season.


CONCLUSIONS
Our data demonstrate a substantial contribution of the influenza season to CF morbidity. Further studies to determine any causal link between influenza infection and CF pulmonary exacerbations are necessary.
Ortiz
Justin R
JR
Division of Pulmonary and Critical Care Medicine, University of Washington Medical Center, Box 356522, 1959 NE Pacific St, Seattle, WA 98195-6522, USA. jrortiz@u.washington.edu
Neuzil
Kathleen M
KM
Victor
John C
JC
Wald
Anna
A
Aitken
Moira L
ML
Goss
Christopher H
CH
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044383:Black People / Q000208:ethnology; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003550:Cystic Fibrosis / Q000453:epidemiology* / Q000208:ethnology / Q000503:physiopathology; D005260:Female; D006630:Hispanic or Latino / Q000208:ethnology; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007251:Influenza, Human / Q000150:complications* / Q000453:epidemiology* / Q000208:ethnology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012042:Registries; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D012621:Seasons; D012720:Severity of Illness Index; D014481:United States / Q000453:epidemiology; D044465:White People / Q000208:ethnology; D055815:Young Adult; D001741:Black or African American