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Differences in the Epidemiological Characteristics and Clinical Outcomes of Pandemic (H1N1) 2009 Influenza, Compared with Seasonal Influenza

Published online by Cambridge University Press:  02 January 2015

Kevin T. Shiley ,
Gregory Nadolski ,
Timothy Mickus ,
Neil O. Fishman  and
Ebbing Lautenbach
Kevin T. Shiley*
Affiliation:
Division of Infectious Diseases, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
Gregory Nadolski
Affiliation:
Department of Radiology, University of Pennsylvania School of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
Timothy Mickus
Affiliation:
Department of Radiology, University of Pennsylvania School of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
Neil O. Fishman
Affiliation:
Division of Infectious Diseases, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
Ebbing Lautenbach
Affiliation:
Division of Infectious Diseases, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania Department of Biostatistics and Epidemiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania Center for Education and Research on Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
*
3rd Floor, Suite D, 3400 Spruce Street, Philadelphia, PA 19103 (shileyk@uphs.upenn.edu)
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Extract

Background.

There are limited data comparing the clinical presentations, comorbidities, and outcomes of patients with infections due to seasonal influenza with patients with infections due to pandemic (H1N1) 2009 influenza.

Objective.

To compare the epidemiological characteristics and outcomes of pandemic (H1N1) 2009 influenza with those of seasonal influenza.

Methods.

A cross-sectional study was conducted among patients who received diagnoses during emergency department and inpatient encounters at 2 affiliated academic medical centers in Philadelphia, Pennsylvania. Cases of seasonal influenza during the period November 1, 2005, through June 1, 2008, and cases of pandemic influenza during the period from May 1, 2009, through August 7, 2009, were identified retrospectively.

Results.

Forty-nine cases of pandemic influenza and 503 cases of seasonal influenza were identified. Patients with pandemic H1N1 were younger (median age, 29 years) than patients with seasonal influenza (median age, 59 years) (P <.001). More patients with pandemic H1N1 (35 [71%] of 49) were African American, compared with patients with seasonal influenza (267 [53%] of 503; P = .02). Several symptoms were more common among patients with pandemic influenza infections than among patients with seasonal influenza infections: cough (98% vs 83%; P = .007), myalgias (71% vs 46%; P = .001), and pleuritic chest pain (45% vs 15%; P < .001). Pregnancy was the only comorbidity that occurred significantly more often in the pandemic influenza group than in the seasonal influenza group (16% vs 1%; P < .001). There were no significant differences in frequencies of deaths of hospitalized patients, intensive care unit admission, or length of hospitalization between groups.

Conclusion.

Other than pregnancy, there were few clinically important differences between infections due to seasonal influenza and those due to pandemic influenza. The greater rate of lower respiratory tract symptoms in pandemic cases might serve to differentiate pandemic influenza from seasonal influenza.

Type
Original Articles
Information
Infection Control & Hospital Epidemiology , Volume 31 , Issue 7 , July 2010 , pp. 676 - 682
Copyright
Copyright © The Society for Healthcare Epidemiology of America 2010

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