Epidemiological, Entomological And Community Determinants Of The 2021 Yellow Fever Outbreak In Wa East District, Ghana: Cross- Sectional Descriptive Outbreak Investigation

Abstract

Objective To describe the epidemiology, ecological determinants and public- health response to a yellow- fever (YF) outbreak in Wa East District (WED), Ghana, and to identify operational gaps to strengthen surveillance and immunisation in high- risk rural settings. Design A cross- sectional descriptive outbreak investigation integrating epidemiological, entomological, vaccination- coverage and community knowledge assessments, conducted under Ghana’s Integrated Disease Surveillance and Response framework. Setting WED, located in the Upper West Region of Ghana, is an agrarian, forest- fringe area bordering the Mole National Park, characterised by limited access to health services and seasonal nomadic movements. Participants All suspected YF cases (N=57) reported between epidemiological weeks 41–46 of 2021; 50 community respondents interviewed for knowledge and awareness and 52 households inspected for entomological indices. Main outcome measures Demographic and clinical characteristics of cases, spatial–temporal distribution, vaccination coverage, Aedes vector indices, community knowledge and awareness levels and response interventions. Results A total of 57 suspected cases (33 males 24 females) were identified, of which 12 (21.1%) were laboratory- confirmed. The case- fatality ratio among confirmed cases was 33.3% (95% CI 9.7% to 65.1%). Most cases occurred in individuals aged 6–30 years and were clustered in the Ducie community. The epidemic curve, based on confirmed cases, showed a single focal wave between epidemiological weeks 41 and 46 of 2021, peaking in week 45 and declining thereafter following intensified outbreak response activities , particularly surveillance and risk communication. Routine YF vaccination coverage was 25% before the outbreak, increasing to 95% after the mass campaign. The district’s composite risk score was 83%, indicating very high transmission risk. Entomological indices (House Index=48.5%, CI=36.1%, Breteau Index=159.6) exceeded WHO thresholds, confirming intense Aedes proliferation. Community awareness was low, with only 22% recognising the viral cause, 16% identifying mosquitoes as vectors and 10% knowing that vaccination prevents YF. Conclusions The outbreak reflected the convergence of ecological vulnerability, low baseline immunity and poor community awareness. Sustained high routine immunisation, structured Aedes surveillance and continuous risk communication are essential to prevent recurrence and advance Ghana’s commitment to the WHO Eliminate Yellow Fever Epidemics strategy.