ZOOM MEETING
https://umich.zoom.us/j/96616169868
Passcode: CSCS [all caps]

Abstract: Environmental pathogen surveillance is a sensitive tool that can detect early-stage outbreaks and has become an important part of the global effort to eradicate polio. While longitudinal environmental surveillance has the potential to inform outbreak dynamics, interpretation can be difficult because the relationship between population infection incidence and viral load in wastewater depends both on the fraction of the population shedding and the time-varying shedding intensity. We developed a mathematical model of time-varying poliovirus shedding intensity consistent with expert opinion across a range of immunization states. Incorporating this shedding model into an infectious disease transmission model, we analyzed quantitative, polymerase chain reaction cycle threshold data from seven sites during the 2013 Israeli polio outbreak. Compared to a constant shedding model, our time-varying shedding model estimated a larger but slower peak (4 weeks later), resulting in a greater fraction of the population vaccinated and a lower cumulative incidence (46% vaccinated and 51% infected by the end of the outbreak, compared to 24% and 74% in the constant shedding scenario). We also estimated the population shed virus for an average of 29 days (95% CI 28-31). Our estimate of polio shedding duration is longer than expert opinion had suggested for a population that was purported to have received three or more inactivated polio vaccine (IPV) doses, indicating that IPV may not affect shedding duration. Using realistic models of time-varying shedding coupled with longitudinal environmental surveillance will improve our understanding of outbreak dynamics of poliovirus or other pathogens, such as SARS-CoV-2.