About our COVID-19 model

In late March 2020, “Stay Home, Stay Healthy” order was issued in Washington State in response to the COVID-19 pandemic. On May 1, a 4-phase reopening plan began. If implemented without interruptions, all types of public interactions would have resumed by July 15. We investigated whether adjunctive prevention strategies will allow less restrictive social distancing avoiding second epidemic waves.


We developed a mathematical model, stratifying the population by age (0-19 years, 20-49 years, 50-69 years, and 70+ years), infection status (susceptible, exposed, asymptomatic, pre-symptomatic, symptomatic, recovered) and treatment status (undiagnosed, diagnosed, hospitalized) to project SARS-CoV-2 transmission during and after the reopening period.

The model is parameterized with demographic and contact data from King County and calibrated to confirmed cases, deaths (overall and by age) and epidemic peak timing. Adjunctive prevention interventions were simulated assuming different levels of pre-COVID physical interactions (pC_PI) restored.


We predict that widespread implementation of “test, trace, and isolate” alone are insufficient to prevent the rapid re-emergence of SARS CoV-2 without moderate physical distancing. However, widespread testing and isolation will allow some relaxation of social distancing relative to current levels (e.g. restoration to 60% pC_PI) without a surge in local cases.

This website is intended to supplment the original article, and allow users to view additional outcomes of our modeled scenarios beyond what was selected for publication.

This page is under construction

Poster citation

Widespread testing, case isolation and contact tracing will not prevent rapid re-emergence of SARS Co-V-2 without continued moderate social distancing: A modeling analysis of King County, WA data. covid19.aids2020.org

Article citation

Widespread testing, case isolation and contact tracing may allow safe school reopening with continued moderate physical distancing: a modeling analysis of King County, WA data

Chloe Bracis, Eileen Burns, Mia Moore, David Swan, Daniel B Reeves, Joshua T Schiffer, Dobromir T Dimitrov

medRxiv 2020.08.14.20174649; doi: https://doi.org/10.1101/2020.08.14.20174649

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