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Complications among adults hospitalized with influenza: a comparison of seasonal influenza and the 2009 H1N1 pandemic
Carrie Reed1,
Sandra S. Chaves1,
Alejandro Perez1,
Tiffany D'Mello1,
Pamala Daily Kirley2,
Deborah Aragon3,
James I. Meek4,
Monica M. Farley5,
Patricia Ryan6,
Ruth Lynfield7,
Craig A. Morin7,
Emily B. Hancock8,
Nancy M. Bennett9,
Shelley M Zansky10,
Ann Thomas11,
Mary Louise Lindegren12,
William Schaffner12, and
Lyn Finelli1
+ Author Affiliations
1Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA
2California Emerging Infections Program (EIP), Oakland, CA
3Colorado Department of Public Health and Environment, Denver, CO
4Connecticut Emerging Infections Program, Yale School of Public Health, New Haven, CT
5Emory University School of Medicine and the Atlanta VAMC, Atlanta, GA
6Maryland EIP, Maryland Department of Health & Mental Hygiene, Baltimore, MD
7Minnesota EIP, Minnesota Department of Health, St. Paul, MN
8New Mexico EIP, New Mexico Department of Health, Santa Fe, NM
9Department of Medicine, University of Rochester School of Medicine and Dentistry, New York State EIP, Rochester, NY
10New York State Department of Health, Albany, NY
11Oregon Public Health Division, Portland, OR
12Tennesee EIP, Tennessee Department of Health, Nashville, TN
Corresponding Author: Carrie Reed, Influenza Division, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, MS A-32, Atlanta, GA 30333, Phone: 404-639-1749, Fax: 404-639-3866, Email: ggj2@cdc.gov
Alternate corresponding author: Sandra Chaves, Influenza Division, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, MS A-32, Atlanta, GA 30333, Phone: 404-639-2797, Fax: 404-639-3866, Email: bev8@cdc.gov
Abstract
Background. Persons with influenza can develop complications that result in hospitalization and death. These are most commonly respiratory-related, but cardiovascular or neurologic complications or exacerbations of underlying chronic medical conditions may also occur. Patterns of complications observed during pandemics may differ from typical influenza seasons, and characterizing variations in influenza-related complications can provide a better understanding of the impact of pandemics and guide appropriate clinical management and planning for the future.
Methods. Using a population-based surveillance system, we compared clinical complications using ICD-9 discharge diagnosis codes in adults hospitalized with seasonal influenza (n=5,270) or 2009 pandemic influenza A(H1N1) (H1N1pdm09) (n=4,962).
Results. Adults hospitalized with H1N1pdm09 were younger (median age 47 years) than those with seasonal influenza (median: 68 years, p<0.01), and differed in the frequency of certain underlying medical conditions. While there was similar risk for many influenza-associated complications, after controlling for age and type of underlying medical condition adults hospitalized with H1N1pdm09 were more likely to have lower respiratory tract complications, shock/sepsis, and organ failure than those with seasonal influenza. They were also more likely to be admitted to the ICU, require mechanical ventilation, or die. Young adults, in particular, had 2?4 times the risk of severe outcomes from H1N1pdm09 than persons of the same ages with seasonal influenza.
Conclusions. While thought of as a relatively mild pandemic, these data highlight the impact of the 2009 pandemic on the risk of severe influenza, especially among younger adults, and the impact this virus may continue to have.
Received January 7, 2014.
Accepted March 13, 2014.
Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2014. This work is written by (a) US Government employee(s) and is in the public domain in the US.
http://cid.oxfordjournals.org/content/early/2014/04/29/cid.ciu285.abstract
Carrie Reed1,
Sandra S. Chaves1,
Alejandro Perez1,
Tiffany D'Mello1,
Pamala Daily Kirley2,
Deborah Aragon3,
James I. Meek4,
Monica M. Farley5,
Patricia Ryan6,
Ruth Lynfield7,
Craig A. Morin7,
Emily B. Hancock8,
Nancy M. Bennett9,
Shelley M Zansky10,
Ann Thomas11,
Mary Louise Lindegren12,
William Schaffner12, and
Lyn Finelli1
+ Author Affiliations
1Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA
2California Emerging Infections Program (EIP), Oakland, CA
3Colorado Department of Public Health and Environment, Denver, CO
4Connecticut Emerging Infections Program, Yale School of Public Health, New Haven, CT
5Emory University School of Medicine and the Atlanta VAMC, Atlanta, GA
6Maryland EIP, Maryland Department of Health & Mental Hygiene, Baltimore, MD
7Minnesota EIP, Minnesota Department of Health, St. Paul, MN
8New Mexico EIP, New Mexico Department of Health, Santa Fe, NM
9Department of Medicine, University of Rochester School of Medicine and Dentistry, New York State EIP, Rochester, NY
10New York State Department of Health, Albany, NY
11Oregon Public Health Division, Portland, OR
12Tennesee EIP, Tennessee Department of Health, Nashville, TN
Corresponding Author: Carrie Reed, Influenza Division, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, MS A-32, Atlanta, GA 30333, Phone: 404-639-1749, Fax: 404-639-3866, Email: ggj2@cdc.gov
Alternate corresponding author: Sandra Chaves, Influenza Division, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, MS A-32, Atlanta, GA 30333, Phone: 404-639-2797, Fax: 404-639-3866, Email: bev8@cdc.gov
Abstract
Background. Persons with influenza can develop complications that result in hospitalization and death. These are most commonly respiratory-related, but cardiovascular or neurologic complications or exacerbations of underlying chronic medical conditions may also occur. Patterns of complications observed during pandemics may differ from typical influenza seasons, and characterizing variations in influenza-related complications can provide a better understanding of the impact of pandemics and guide appropriate clinical management and planning for the future.
Methods. Using a population-based surveillance system, we compared clinical complications using ICD-9 discharge diagnosis codes in adults hospitalized with seasonal influenza (n=5,270) or 2009 pandemic influenza A(H1N1) (H1N1pdm09) (n=4,962).
Results. Adults hospitalized with H1N1pdm09 were younger (median age 47 years) than those with seasonal influenza (median: 68 years, p<0.01), and differed in the frequency of certain underlying medical conditions. While there was similar risk for many influenza-associated complications, after controlling for age and type of underlying medical condition adults hospitalized with H1N1pdm09 were more likely to have lower respiratory tract complications, shock/sepsis, and organ failure than those with seasonal influenza. They were also more likely to be admitted to the ICU, require mechanical ventilation, or die. Young adults, in particular, had 2?4 times the risk of severe outcomes from H1N1pdm09 than persons of the same ages with seasonal influenza.
Conclusions. While thought of as a relatively mild pandemic, these data highlight the impact of the 2009 pandemic on the risk of severe influenza, especially among younger adults, and the impact this virus may continue to have.
Received January 7, 2014.
Accepted March 13, 2014.
Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2014. This work is written by (a) US Government employee(s) and is in the public domain in the US.
http://cid.oxfordjournals.org/content/early/2014/04/29/cid.ciu285.abstract