A quantitative framework to define the end of an outbreak: application to Ebola Virus Disease

Bimandra A Djaafara; Natsuko Imai; Esther Hamblion; Benido Impouma; Christl A Donnelly; Anne Cori

Our study also shows that the reporting rate plays an important role in assessing the EO, and that, in line with results by Thompson et al. (21) , a low reporting rate would lead to a lower confidence in declaring the end of an EVD outbreak at day 42 after the outcome of the last case, i.e. using the current WHO criterion. Hence, for outbreaks with low reporting rates, a longer waiting time would be needed to declare the EO. However, we found that the dependency on the reporting rate became negligible as the onset-to-outcome delay period decreases. This suggests that using the onset day, rather than the outcome day, as the baseline of the waiting time should be considered as it may be more robust to variability in the outbreak context. This would also account for the three possible scenarios for the last detected case which could include any delays in testing of the last detected case or delays in burial (8) .