Understanding the early dynamics of the 2014 porcine epidemic diarrhea virus (PEDV) outbreak in Ontario using the incidence decay and exponential adjustment (IDEA) model

Greer, Amy L.; Spence, Kelsey; Gardner, Emma

The to approximate the epidemic final size, epidemic trajectory, and time at which the final size would be reached using only 3 generations worth of simple case count data assuming a generation time of seven days (Fig. 4) . For veterinary epidemiologists and others tasked with providing situational awareness and updates to industry during an infectious disease outbreak, the ability to reasonably project forward in time an estimate of the total number of cases expected and the time at which the epidemic is expected to peak would be an incredibly useful application. In this instance, the ability to "nearcast" with some certainty would better allow emergency operations personnel to budget the physical and human resources that would be required to see an outbreak through to completion. Given the uncertainty around the possible generation time estimates, we also examined two alternative scenarios whereby we assumed a longer generation time of 10 or 13 days. In both cases, we found that the model was less accurate at projecting the expected course of the PEDV outbreak using three generations of data assuming a generation time of 10 or 13 days than in the base case that assumed a generation time of seven days (Figs. 4 and 5). This suggests that even without accounting for the possibility of a prolonged duration of viral shedding within some swine, the lower generation time estimate is sufficient to capture the dynamics of the outbreak.