An Epidemic Model for Multi-Intervention Outbreaks

Modeling is an important tool to utilize at the beginning of an infectious disease outbreak, as it allows estimation of parameters—such as the basic reproduction number, R 0 —that can be used to postulate how the outbreak may continue to spread. However, there exist many challenges that need to be accounted for, such as an unknown first case date, retrospective reporting of ‘probable’ cases, changing dynamics between case count and death count trends, and the implementation of multiple control efforts and their delayed or diminished effects. Using the near-daily data provided from the recent outbreak of Sudan ebolavirus in Uganda as a case study, we create a model and present a framework aimed at overcoming these aforementioned challenges. The impact of each challenge is examined by comparing model estimates and fits throughout our framework. Indeed, we found that allowing for multiple fatality rates over the course of an outbreak generally resulted in better fitting models. On the other hand, not knowing the start date of an outbreak appeared to have large and non-uniform effects on parameter estimates, particularly at the beginning stages of an outbreak. While models that did not account for the decaying effect of interventions on transmission underestimated R 0 , all decay models run on the full dataset yielded precise R 0 estimates, demonstrating the robustness of R 0 as a measure of disease spread when examining data from the entire outbreak.