887. Comparing Clinical Characteristics Between Hospitalized Adults With Laboratory-confirmed Influenza A and B Virus Infection, 2005-2012
Session: Poster Abstract Session: Respiratory Infections
Friday, October 4, 2013
Room: The Moscone Center: Poster Hall C

Influenza B infections are often perceived as milder than influenza A infections. Although studies have shown similar clinical features between patients infected with seasonal influenza A and B viruses in outpatients and pediatric patients, no comparison was performed in hospitalized adults. Studies also suggested that oseltamivir may be less effective at reducing fever in pediatric outpatients with influenza B.  We compared outcomes among hospitalized adults and those who were treated with oseltamivir by virus type.


We identified adults hospitalized with laboratory-confirmed influenza from 2005–06 through 2011–12 influenza seasons (excluding the 2009 pandemic) using the Influenza Hospitalization Surveillance Network (FluSurv-NET).  We compared clinical characteristics, antiviral treatment, length of hospitalization and hospital mortality between patients infected with influenza A and B viruses and among patients treated with oseltamivir.


During study period, 10,125 (83%) influenza A and 2,100 (17%) influenza B –associated adult hospitalizations were identified.  In adults aged ≥ 65 years, no significant differences in clinical characteristics, length of hospital stay, ICU admission or death were found by influenza type.  Adults aged 18-64 years with influenza A infection were more often admitted to the ICU (OR=1.3; p=0.01) and required mechanical ventilation (OR=1.4, p=0.01) than those with influenza B; no other differences including length of hospitalization and death were observed in this age group.  Antiviral treatment was prescribed less frequently to patients with influenza B infection (A: 73% vs. B: 56%, p<0.01).  After controlling for age, underlying medical condition and ICU admission, we found no differences in length of hospital stay (aHR = 0.97; 95% CI: 0.9-1.0) or mortality (aOR = 0.87; 95% CI, 0.6-1.1) among adults treated with oseltamivir by influenza virus type.


Influenza A and B virus infection resulted in similar hospital courses for adults, although influenza A infections may cause more ICU admissions for some adults <65 years of age.  Outcomes were similar among oseltamivir treated adults with influenza A and B infections.  All patients hospitalized with influenza should receive early antiviral treatment regardless of virus type. 

Su Su, MSc, MPH1,2, Sandra Chaves, MD, MSc3, Alejandro Perez, MPH3, Tiffany D'mello, MPH, MBA3, Pam Daily, MPH4, Lisa Miller, MD, MSPH5, Kimberly Yousey-Hindes, MPH, CPH6, Monica Farley, MD7, Leslie Tengelsen, PhD, DVM8, Meghan Harris, MPH, MPA9, Patricia Ryan, MS10, Craig Morin, MPH11, Ruth Lynfield, MD12, Emily Hancock, MS13, Shelley M. Zansky, PhD14, Brian Fowler, MPH15, Kristy Bradley, DVM, MPH16, Ann Thomas, MD, MPH17, Ananda Bandyopadhyay, MBBS, MPH18, Vickie Horan19, William Shaffner20, Mary Lou Lindegren20 and Alicia Fry, MD, MPH21, (1)Atlanta Research and Education Foundation, Atlanta, GA, (2)Epidemiology and Prevention Branch, Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, (3)Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, (4)California Emerging Infections Program, Oakland, CA, (5)Colorado Department of Public Health and Environment, Denver, CO, (6)Emerging Infections Program, Yale, New Haven, CT, (7)Emory Univ. & VAMC, Decatur, GA, (8)Idaho Division of Health, Boise, ID, (9)Iowa Department of Public Health, Des Moines, IA, (10)Maryland Department of Health and Mental Hygiene, Baltimore, MD, (11)Minnesota Department of Health, St. Paul, MN, (12)Acute Disease Investigation and Control, Minnesota Department of Health, St. Paul, MN, (13)New Mexico Dept. Health, Sante Fe, NM, (14)Emerging Infections Program, New York State Department of Health, Albany, NY, (15)Ohio Department of Health, Columbus, OH, (16)Oklahoma State Department of Health, Oklahoma City, OK, (17)Oregon Health Authority, Portland, OR, (18)Gates Foundation, Seattle, WA, (19)South Dakota Department of Health, Pierre, SD, (20)Vanderbilt University School of Medicine, Nashville, TN, (21)Centers for Disease Control and Prevention (CDC), Atlanta, GA


S. Su, None

S. Chaves, None

A. Perez, None

T. D'mello, None

P. Daily, None

L. Miller, None

K. Yousey-Hindes, None

M. Farley, None

L. Tengelsen, None

M. Harris, None

P. Ryan, None

C. Morin, None

R. Lynfield, None

E. Hancock, None

S. M. Zansky, None

B. Fowler, None

K. Bradley, None

A. Thomas, None

A. Bandyopadhyay, None

V. Horan, None

W. Shaffner, None

M. L. Lindegren, None

A. Fry, None

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