Large Pertussis Outbreak in Rural Canada: Lessons Learned from Haida Gwaii

Objective: To present characteristics of and response to a large outbreak of pertussis on Haida Gwaii, BC, in 2014.

Design: Quantitative descriptive review.

Setting: Haida Gwaii, a remote island archipelago located 100 km off of British Columbia's west coast.

Participants: All patients presenting with symptoms evaluated for pertussis on Haida Gwaii between February and August 2014.

Main Outcome Measures: The primary outcome measures included the demographic characteristics, time course, and morbidity of the outbreak. The secondary outcome measures included the laboratory result reports, the effects on clinician workload, and the treatment and prophylaxis practices. Statistical analysis for significance of pertussis severity and immunization status was performed with a maximum-likelihood framework.

Results: Between February and August 2014, out of 873 clinical encounters, 579 patients were seen for pertussis-related care. Of these, 260 patients were reported to public health for case identification, contact tracing, and follow-up. There were 123 cases of probable and confirmed pertussis, a case rate of 2795 cases per 100 000 population. Of these 123 cases, 91 had a cough of more than 2 weeks' duration. A subset of patients presented with mild symptoms, atypical of pertussis. Nasopharyngeal swabs were collected on 221 occasions, 378 antibiotic prescriptions were written, and 248 prophylactic immunizations were given. The odds ratio that previous immunization protected against the development of classic pertussis was 0.23; however, statistical significance was not reached ( = .112).

Conclusion: Pertussis is resurging. Physicians need to remain vigilant for its characteristic symptoms. Clear and standardized criteria for the declaration of an outbreak should be developed. To contain an outbreak, it is crucial to deploy resources commensurate with disease activity while coordinating public health and primary care. More research into why large outbreaks continue to occur, why endemic rates continue to rise, and how these can be most effectively prevented is essential.