1124. Clinical Characteristics, Risk Factors, and Outcome of  Pandemic H1N1 Influenza A (pH1N1)-associated Pneumonia: Experience of the Public Health Agency of Canada/Canadian Institutes of Health Research Influenza Research Network (PCIRN) Serious Outcomes Surveillance (SOS) Network
Session: Poster Abstract Session: Influenza and H1N1 Diagnosis, Epidemiology, and Viral Outcome
Saturday, October 22, 2011
Room: Poster Hall B1

The SOS Network conducts active surveillance for lab-confirmed influenza in hospitalized Canadian adults to determine disease burden, clinical outcomes and vaccine effectiveness. During the second (fall) wave of the 2009 H1N1 pandemic, we evaluated the clinical characteristics, risk factors, and outcomes of CXR-confirmed pH1N1- associated pneumonia (pH1N1-P).


The PCIRN SOS Network comprises 8 hospitals and ~5000 beds in 5 provinces. Nurses conducted active surveillance for influenza in admitted adults 10/1/09-4/30/10. All patients with respiratory infection, community acquired pneumonia, exacerbation of COPD/asthma, sepsis, or febrile cardiac disease had NP swab for influenza PCR. Clinical, radiographic, and outcome data was collected on patients with pH1N1-P. Multivariable logistic regression was used to assess risk factors for pH1N1-P among cases of pH1N1.


378 cases of lab-confirmed pH1N1 were enrolled; 171 (45%) had pH1N1-P. Mean age of pH1N1-P was 46.9 years (16-87y), 48% were female and 86.6% had ≥ 1 comorbidity. Only 33.3 and 68.4% of cases met PHAC or CDC influenza-like-illness case definitions, respectively. 67% presented with bilateral CXR abnormalities and 76.3% had bilateral pneumonia during hospitalization; 37% had pleural effusions. Patients with H1N1-P had longer lengths of stay than patients without pneumonia (mean 17.7d; range 1-254d v 7.7d; 1-84d; p<.0001), were more likely to require ICU (48 v 16%; p<.0001), or be ventilated (39.8 v 10.1%, p<.0001), to experience a complication (62.6 v 23.2%; p<.0001), and to die (12.3 v 3.9%; p=.01). Only 11.1 and 11.7% had positive bacterial blood or sputum cultures. Early treatment with antivirals nor antibiotics impacted the risk of need for ICU admission or death. Risk factors for pH1N1-P by multivariate logistic regression were Aboriginal ethnicity (3.5 v 1.0%; OR 9.2; 95%CI 1.4 – 58.8), and current or past malignancy (20.5 v 12.6%, OR 1.97; 95% CI 1.01-3.85).  


45% of adults with lab-confirmed pH1N1 hospitalized in the SOS Network had associated pneumonia; only ~11% had positive bacterial cultures. 48% required ICU and 12% died. Malignancy and Aboriginal status were risk factors for pH1N1-P.

Subject Category: V. Virology including clinical and basic studies of viral infections, including hepatitis

Nick Costain, BSc1, Thomas Marrie, MD1, Allison McGeer, MD2, Karen Green, MSc3, Stefan P. Kuster, MD4, Jennie Johnstone, MD5, Mark Loeb, MD, MSc5, Ardith Ambrose, RN6, Todd Hatchette, MD7, Margaret L. Russell, MD8, Elizabeth Henderson, PhD9, Sylvie Trottier, MD10, Guy Boivin, MD10, Anne McCarthy, MD11,12, Grant Stiver, MD13, Scott Halperin, MD14, Joanne Langley, MD14 and Shelly McNeil, MD14, (1)Faculty of Medicine, Dalhousie University, Halifax, NS, Canada, (2)Department of Infection Prevention and Control, Mount Sinai Hospital, Toronto, ON, Canada, (3)Toronto Invasive Bacterial Diseases Network (TIBDN), Mt. Sinai Hospital, Toronto, NS, Canada, (4)Mount Sinai Hospital, Toronto, ON, Canada, (5)McMaster University, Hamilton, ON, Canada, (6)Canadian Center for Vaccinology, IWK Health Centre, Dalhousie University, Halifax, NS, Canada, (7)Canadian Center for Vaccinology, IWK Health Center and Capital Health, Halifax, NS, Canada, (8)Community Health Sciences, University of Calgary, Calgary, AB, Canada, (9)Alberta Health Services, Calgary, AB, Canada, (10)Hopital Laval, Ste-Foy, QC, Canada, (11)G12, Ottawa Hospital General Campus, Ottawa, ON, Canada, (12)Ottawa Hospital General Campus, Ottawa, ON, Canada, (13)University of British Columbia, Vancouver General, Vancouver, BC, Canada, (14)Canadian Center for Vaccinology, IWK Health Centre and Capital Health, Dalhousie University, Halifax, NS, Canada


N. Costain, None

T. Marrie, None

A. McGeer, None

K. Green, None

S. P. Kuster, None

J. Johnstone, None

M. Loeb, None

A. Ambrose, None

T. Hatchette, None

M. L. Russell, None

E. Henderson, None

S. Trottier, None

G. Boivin, None

A. McCarthy, None

G. Stiver, None

S. Halperin, None

J. Langley, None

S. McNeil, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.