Pertussis outbreak investigation of Dara Malo district, Gamo Administrative Zone, Southern Nations, Nationalities and Peoples Region, Southern Ethiopia

Abstract Background: The aim of this outbreak investigation was to verify and describe a pertussis outbreak in the Dara Malo district of Ethiopia. Method: a descriptive cross-sectional study was conducted using district Public Health Emergency and Management (PHEM) surveillance data and outbreak management field reports. Stratified attack rates and fatality for pertussis are described. Systemic problems leading to the outbreak are explored and narrated. A modified CDC pertussis case definition was employed with polymerase chain reaction used to confirm cases. Results: From September 2018 to January 2019, 1840 suspected, probable and confirmed pertussis cases and six deaths were identified. Pertussis cases ranged from 1 month to 51 years in age and outbreak occurred in 14 out of the 24 villages of Dara Malo district. The overall attack rate was 1708 per 100,000 population with a fatality rate of 3.3 per 1,000 pertussis cases. The highest attack rate of 12,689/100,000 was seen in infants. Investigations suggest low vaccine coverage and cold chain management system leading to low vaccine potency as the most likely reason for the outbreak. in these community were: low pentavalent three vaccination coverage and non- functional. In addition, poor implementation of surveillance programs, poor health seeking behavior of the community may have led to delayed and suboptimal responses to the outbreak. Conclusion: There is an urgent need to build capacity to strengthen routine vaccination services capacitate health workers to manage outbreaks. In addition, improving the maintenance of cold chain must be prioritised. Other LMICs, are urged to take lessons learnt from this outbreak and strengthen their own vaccination programs.