Epidemiology and control of Ebola Virus Disease (EVD) in Sierra Leone: analysis of data from the Médecins Sans Frontières (MSF) response, 2014-15

Aims and Objectives This thesis stems from work conducted with Médecins Sans Frontières in Sierra Leone, during the 2014- 2015 Ebola virus disease (EVD) outbreaks. The thesis addresses 3 main public health knowledge gaps and aims to improve the response to future EVD outbreaks by: 1) Understanding the factors that influenced EVD transmission and community compliance with con- trol measures; 2) Estimating the performance of the WHO EVD case definition, and what components could improve it; 3) Estimating the design effect and mortality rates, and discussing how to improve future surveys for highly-clustered diseases. Methods The methods corresponding to each gap were: 1) A mixed-methods study in one village experiencing sustained transmission in Sierra Leone; 2) A review and meta-analysis exploring performance of WHO EVD case definitions against laboratory confirmed EVD; 3) Two population-based clustered surveys, in Sierra Leone. Results Study 1 identified that non-compliance with public health guidelines was a consequence of the failure of the response to orientate itself according to the needs and values of the community. Study 2 estimated that the WHO EVD case definition performed sub-optimally to identify cases (sen- sitivity 81·5% (74·1-87·2%); specificity 35·7% (28·5-43·6%)). Inclusion of intense fatigue as a key symptom and contact history could improve performance, but these changes would require collabora- tion with, and trust of, affected communities. Study 3 identified a high degree of clustering in community-based surveys of EVD, this contributed to imprecise mortality estimates, which have limited utility when assessing the impact of disease. Estimated the design effect along with methodological suggestions provided can inform future surveys for similar highly clustered diseases. Conclusion The thesis highlights that outbreak patterns are linked to social and cultural environments. Community influence key public health practices (i.e. case definitions). Recognition of transmission risks from responding organization requires a respectful and compassionate approach, understanding of social norms and adapted community-lead interventions.