Open Access Open Badges Research article

Ethnic disparities in acquiring 2009 pandemic H1N1 influenza: a case–control study

Debeka Navaranjan12, Laura C Rosella123*, Jeffrey C Kwong1234, Michael Campitelli3 and Natasha Crowcroft12

Author Affiliations

1 Department of Public Health Sciences, Public Health Ontario, 480 University Avenue, Suite 300, Toronto, Ontario M5G 1 V2, Canada

2 Dalla Lana School of Public Health, University of Toronto, 155 College Street, Toronto, Ontario M5T 3 M7, Canada

3 Institute for Clinical Evaluate Sciences, 2075 Bayview Avenue, Toronto, Ontario M4N 3 M5, Canada

4 Department of Family and Community Medicine, University of Toronto, 500 University Avenue, Toronto, Ontario M5G 1 V7, Canada

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BMC Public Health 2014, 14:214  doi:10.1186/1471-2458-14-214

Published: 1 March 2014



Novel risk factors were associated with the 2009 pandemic A/H1N1 virus (pH1N1). Ethnicity was among these risk factors. Ethnic disparities in hospitalization and death due to pH1N1 were noted. The purpose of this study is to determine whether there are ethnic disparities in acquiring the 2009 pandemic H1N1.


We conducted a test-negative case–control study of the risk of pH1N1 infection using data from Ontario, Canada. Cases were laboratory confirmed to have influenza using reverse-transcriptase polymerase chain reaction (RT-PCR), and controls were obtained from the same population and were RT-PCR negative. Multivariate logistic regression was used to determine the association between ethnicity and pH1N1 infection, while adjusting for demographic, clinical and ecological covariates.


Adult cases were more likely than controls to be self-classified as East/Southeast Asian (OR = 2.59, 95% CI 1.02-6.57), South Asian (OR = 6.22, 95% CI 2.01-19.24) and Black (OR = 9.72, 95% CI 2.29-41.27). Pediatric cases were more likely to be self-identified as Black (OR = 6.43, 95% CI 1.83-22.59). However, pediatric cases without risk factors for severe influenza infection were more likely to be South Asian (OR 2.92, 95% CI 1.11-7.68), Black (OR 16.02, 95% CI 2.85-89.92), and West Asian/Arab, Latin American or Multi-racial groups (OR 3.09 95% CI 1.06-9.00).


pH1N1 cases were more likely to come from certain ethnic groups compared to test-negative controls. Insights into whether these disparities arise due to social or biological factors are needed in order to understand what approaches can be taken to reduce the burden of a future influenza pandemic.

Influenza; Ethnicity; Epidemiology