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Am J Infect Control. 2014 Jan;42(1):7-11. doi: 10.1016/j.ajic.2013.06.018. Epub 2013 Oct 30.

Hospital-onset influenza hospitalizations--United States, 2010-2011.

Author information

  • 1Epidemiology and Prevention Branch, Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA. Electronic address:
  • 2Epidemiology and Prevention Branch, Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA.
  • 3Colorado Department of Public Health and Environment, Denver, CO.
  • 4Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY.
  • 5Rhode Island Department of Health, Providence, RI.
  • 6Georgia Division of Public Health, Georgia Emerging Infections Program, Emory University, Atlanta, GA.
  • 7Ohio Department of Health, Columbus, OH.
  • 8Oklahoma State Department of Health, Oklahoma City, OK.
  • 9New Mexico Department of Health, Santa Fe, NM.
  • 10Minnesota Department of Health, St Paul, MN.
  • 11California Emerging Infections Program, Oakland, CA.
  • 12Maryland Department of Health and Mental Hygiene, Baltimore, MD.
  • 13Department of Preventive Medicine, Vanderbilt University School of Medicine, Nashville, TN.
  • 14Michigan Department of Community Health, Lansing, MI.
  • 15Idaho Department of Health and Welfare, Boise, ID.
  • 16Oregon Public Health Division, Portland, OR.
  • 17Salt Lake Valley Health Department, Salt Lake City, UT.
  • 18Connecticut Emerging Infections Program, Yale School of Public Health, New Haven, CT.



Seasonal influenza is responsible for more than 200,000 hospitalizations each year in the United States. Although hospital-onset (HO) influenza contributes to morbidity and mortality among these patients, little is known about its overall epidemiology.


We describe patients with HO influenza in the United States during the 2010-2011 influenza season and compare them with community-onset (CO) cases to better understand factors associated with illness.


We identified laboratory-confirmed, influenza-related hospitalizations using the Influenza Hospitalization Surveillance Network (FluSurv-NET), a network that conducts population-based surveillance in 16 states. CO cases had laboratory confirmation ≤ 3 days after hospital admission; HO cases had laboratory confirmation > 3 days after admission.


We identified 172 (2.8%) HO cases among a total of 6,171 influenza-positive hospitalizations. HO and CO cases did not differ by age (P = .22), sex (P = .29), or race (P = .25). Chronic medical conditions were more common in HO cases (89%) compared with CO cases (78%) (P < .01), and a greater proportion of HO cases (42%) than CO cases (17%) were admitted to the intensive care unit (P < .01). The median length of stay after influenza diagnosis of HO cases (7.5 days) was greater than that of CO cases (3 days) (P < .01).


HO cases had greater length of stay and were more likely to be admitted to the intensive care unit or die compared with CO cases. HO influenza may play a role in the clinical outcome of hospitalized patients, particularly among those with chronic medical conditions.

Published by Mosby, Inc.


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[PubMed - indexed for MEDLINE]
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