Open Access Highly Accessed Research article

Bordetella pertussis in sporadic and outbreak settings in Alberta, Canada, July 2004 – December 2012

Sumana Fathima1, Christina Ferrato1, Bonita E Lee2*, Kimberley Simmonds34, Lin Yan5, Shamir N Mukhi6, Vincent Li5, Linda Chui25 and Steven J Drews17

Author Affiliations

1 Provincial Laboratory for Public Health (ProvLab) Calgary Site, Calgary, AB, Canada

2 University of Alberta, Edmonton, AB, Canada

3 Alberta Health, Edmonton, AB, Canada

4 University of Calgary, Department of Community Health Sciences, Calgary, AB, Canada

5 Provincial Laboratory for Public Health (ProvLab) Edmonton Site, Edmonton, AB, Canada

6 Canadian Network for Public Health Intelligence, Public Health Agency of Canada, Winnipeg, MB, Canada

7 Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, AB, Canada

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BMC Infectious Diseases 2014, 14:48  doi:10.1186/1471-2334-14-48

Published: 30 January 2014

Abstract

Background

ProvLab Alberta provides all laboratory testing for Bordetella pertussis including sporadic cases and outbreak investigations through collaborations with provincial public health partners. We describe B. pertussis activity in Alberta from July 2004 to December 2012.

Methods

Laboratory testing for pertussis was analyzed using interpreted laboratory data that was generated by DIAL, a secure web-based platform. Duplicate specimens from the same individual ≤90 days were excluded to generate a case-based dataset. Immunization status of confirmed pertussis cases from the provincial immunization repository was reviewed.

Results

Overall, 7.1% of suspected pertussis cases tested positive with a higher positivity rate in outbreak as compared to sporadic setting. Annual variations in sporadic pertussis cases were observed across the province with higher positivity rates in 2005, 2008, 2009 and 2012. A significantly higher positivity rate was observed in a northern region of Alberta. While the positivity rate in sporadic setting was highest in adolescents aged 10 to <15 years old (14.8%), population-based disease burden was highest in young children <5 years old. Of the 81.6% (n = 1,348) pertussis cases with immunization records, 48.3% were up-to-date with immunization. The pertussis cases that were up-to-date with their immunization were older (median age 12.9 years) as compared to those with incomplete (median age 9.7 years) or no pertussis immunization (median age 3.8 years).

Conclusions

Cyclic pattern of annual pertussis activity with geographic variation was observed in Alberta with no obvious case finding effect from outbreak investigations. The high positivity rates in adolescents suggested an underestimation of disease burden in this age group.

Keywords:
Pertussis; Outbreaks; Epidemiology