Pertussis outbreak investigation in Northwest Ethiopia: A community based study

Pertussis or whooping cough is a vaccine-preventable, highly contagious, respiratory illness caused by Bordetella pertussis or Bordetella parapertussis. Infants and young children have remained most susceptible to pertussis-related morbidity and mortality. The aim of this study was to investigate pertussis infection and analyze the associated factors involved in the occurrence of the cases.

Community-based case-control was conducted in Dahena district, Northwest Ethiopia, from March 27-April 30, 2019. All cases ages 1-18 years old were identified by using the clinical standard case definition of pertussis adopted from World Health Organization (WHO). Data was collected using a structured questionnaire via face-to-face interviews. The data collected was cleaned, coded and entered into Epi info version 7.2.1.0 and exported to SPSS version 23 for statistical analysis. Bivariable and multivariable logistic regression analysis were employed to identify predictors. Factors with a p-value of < 0.05 were considered as independent risk factors of pertussis infection in multivariable logistic regression analysis.

A total of 122 pertussis cases were enrolled from the Azila cluster of the Dahena district. Of these figures, 64 (52.5%) were females. The overall attack rate (AR) of pertussis cases in the cluster was 8.6/10000 population. The sex-specific AR of females was 8.9/10000 population. The multivariable logistic regression analysis showed that; being unvaccinated 4.17 (AOR, 4.17, 95% CI, 1.914-9.091), contact to cases 2.93 (AOR: 2.93, 95% CI 1.223-6.996), and living in a house with no window 2.6 (AOR: 2.6(95% CI 1.071 to 6.322) were the independent significantly risk factors for pertussis infection.

The contributing factor for pertussis infection was associated with case-contact, living in the house without windows and being unvaccinated. Wag Hemra Zone and Dahena district health office should encourage the vaccination activities of the cluster health center and awareness for the community should be practiced to limit disease transmission.