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

There is significant variability in the documented incubation period and infectious period for PEDV within the published literature [7, 23, 25] . It is thought that some proportion of animals can continue to shed the virus for up to 20-30 days after infection [25] . In this case, the expected generation time would be longer than the seven days that we have used in this study. However, we expect that the highest risk of direct farm-to-farm transmission likely occurs during the initial infection period for a farm/herd when infection rates are still low, clinical symptoms have not yet become widespread, a veterinarian has not yet submitted samples to the laboratory, and therefore enhanced biosecurity measures are not yet in place. This likely describes the first seven days of a farm level outbreak and therefore, this is how we justify our lower limit generation time of seven days. We would expect that as the outbreak becomes more obvious within a specific herd even though shedding may continue to occur for long periods of time, between farm transmission risk is decreased due to enhanced biosecurity.