Risk factors for hospitalization and severe outcomes of 2009 pandemic H1N1 influenza in Quebec, Canada
Article first published online: 9 FEB 2011
© 2011 Blackwell Publishing Ltd
Influenza and Other Respiratory Viruses
Volume 5, Issue 4, pages 247–255, July 2011
How to Cite
Gilca, R., De Serres, G., Boulianne, N., Ouhoummane, N., Papenburg, J., Douville-Fradet, M., Fortin, É., Dionne, M., Boivin, G. and Skowronski, D. M. (2011), Risk factors for hospitalization and severe outcomes of 2009 pandemic H1N1 influenza in Quebec, Canada. Influenza and Other Respiratory Viruses, 5: 247–255. doi: 10.1111/j.1750-2659.2011.00204.x
- Issue published online: 9 JUN 2011
- Article first published online: 9 FEB 2011
- Accepted 20 December 2010. Published Online 8 February 2011.
- risk factors
Please cite this paper as: Gilca et al. (2011) Risk Factors for Hospitalization and Severe Outcomes of 2009 Pandemic H1N1 Influenza in Quebec, Canada. Influenza and Other Respiratory Viruses 5(4), 247–255
Background/ Objective This case–control study was carried out to estimate risk factors associated with hospitalizations and severe outcomes [intensive care unit (ICU) admission or death] among patients with illness because of laboratory-confirmed 2009 pandemic A/H1N1 virus (pH1N1) during the first wave of pH1N1 activity in the province of Quebec, Canada.
Patients/ Methods We collected epidemiologic information by phone using a standardized questionnaire from patients with laboratory-confirmed pH1N1 illness during the first spring/summer pandemic wave in Quebec, Canada. Risk factors associated with hospitalization were assessed by comparing hospitalized to community cases and for ICU admission or death through comparison with hospitalized cases.
Results Cases (321 hospitalized patients including 47 ICU admissions and 15 deaths) were compared to controls (395 non-hospitalized patients) by using multivariable logistic regression adjusted for gender, age, education, being a health care worker, smoking, seasonal influenza vaccination, delay to consultation, antiviral use before admission, pregnancy, underlying medical conditions, and obesity. Age <5 years, underlying medical conditions (neuromuscular, cardiac, pulmonary, and renal conditions, diabetes, asthma, and other), and delayed consultation were associated with hospitalization. The strongest association with hospitalization was observed for neuromuscular disorders. Antiviral medication before hospital admission protected against severe disease. Association of obesity with hospitalization was not significant after adjustment in multivariable analysis. Among hospitalized patients, age ≥60 years and immune suppression were associated with death.
Conclusions Previously identified risk factors for seasonal influenza were also associated with increased risk of severe pH1N1 outcomes. The independent role of obesity needs to be further defined.