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.

Model

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.

Conclusions

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

Article references

  1. COVID-19 Dashboard by the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University (JHU) https://coronavirus.jhu.edu/map.html

  2. Coronavirus in the U.S.: Latest Map and Case Count. The New York Times (2020). https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html#states.

  3. Birnbaum, M. Reopened schools in Europe and Asia have largely avoided coronavirus outbreaks. They have lessons for the U.S. The Washington Post (2020). https://www.washingtonpost.com/world/europe/schools-reopening-coronavirus/2020/07/10/865fb3e6-c122-11ea-8908-68a2b9eae9e0_story.html.

  4. Holshue, M. L. et al. First Case of 2019 Novel Coronavirus in the United States. N Engl J Med 382, 929-936 (2020).

  5. Washington Governor Jay Inslee webpage. Inslee announces “Stay Home, Stay Healthy” order < https://www.governor.wa.gov/news-media/inslee-announces-stay-home-stay-healthy%C2%A0order>.

  6. O’Sullivan, J. Inslee extends coronavirus stay-home order through May 31, outlines plan to reopen Washington in phases. The Seattle Times. https://www.seattletimes.com/seattle-news/politics/inslee-announces-extended-stay-home-order-outlines-plan-to-reopen-washington-in-phases/.

  7. Washington Department of Health. County status and Safe Start application process. https://coronavirus.wa.gov/what-you-need-know/county-status-and-safe-start-application-process.

  8. Pei, S. & Shaman, J. Initial Simulation of SARS-CoV2 Spread and Intervention Effects in the Continental US. medRxiv, 2020.2003.2021.20040303 (2020).

  9. Ferguson, N. M. et al. Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand. https://www.imperial.ac.uk/mrc-global-infectious-disease-analysis/covid-19/report-9-impact-of-npis-on-covid-19/.

  10. Chinazzi, M. et al. The effect of travel restrictions on the spread of the 2019 novel coronavirus (COVID-19) outbreak. Science 368, 395 (2020).

  11. Lourenco, J. et al. Fundamental principles of epidemic spread highlight the immediate need for large-scale serological surveys to assess the stage of the SARS-CoV-2 epidemic. medRxiv, 2020.2003.2024.20042291 (2020).

  12. Kissler, S. M., Tedijanto, C., Goldstein, E., Grad, Y. H. & Lipsitch, M. Projecting the transmission dynamics of SARS-CoV-2 through the postpandemic period. Science 368, 860 (2020).

  13. Kucharski, A. J. et al. Effectiveness of isolation, testing, contact tracing, and physical distancing on reducing transmission of SARS-CoV-2 in different settings: a mathematical modelling study. The Lancet Infectious Diseases (2020).

  14. Centers for Disease Control and Prevention. COVID-19 Pandemic Planning Scenarios. https://www.cdc.gov/coronavirus/2019-ncov/hcp/planning-scenarios.html#box.

  15. Public Health - Seattle & King County. COVID-19 data dashboard. (2020). https://kingcounty.gov/depts/health/covid-19/data.aspx.

  16. Bedford, T. et al. Cryptic transmission of SARS-CoV-2 in Washington State. medRxiv, 2020.2004.2002.20051417 (2020).

  17. Thakkar, N. & Famulare, M. COVID-19 transmission was likely rising through April 22 across Washington State. Institute for Disease Modeling (2020). https://covid.idmod.org/#/ResearchandReports.

  18. Havers, F. P. et al. Seroprevalence of Antibodies to SARS-CoV-2 in 10 Sites in the United States, March 23-May 12, 2020. JAMA Intern Med.

  19. Beigel, J. H. et al. Remdesivir for the Treatment of Covid-19 – Preliminary Report. N Engl J Med (2020).

  20. Byambasuren, O. et al. Estimating the extent of asymptomatic COVID-19 and its potential for community transmission: systematic review and meta-analysis. medRxiv, 2020.2005.2010.20097543 (2020).

  21. Poletti, P. et al. Probability of symptoms and critical disease after SARS-CoV-2 infection. arXiv.org > q-bio > arXiv:2006.08471 (2020).

  22. Howard, J. Coronavirus spread by asymptomatic people 'appears to be rare,' WHO official says. CNN Health. https://www.cnn.com/2020/06/08/health/coronavirus-asymptomatic-spread-who-bn/index.html.

  23. Lee, S. et al. Clinical Course and Molecular Viral Shedding Among Asymptomatic and Symptomatic Patients With SARS-CoV-2 Infection in a Community Treatment Center in the Republic of Korea. JAMA Intern Med (2020).

  24. Zhou, R. et al. Viral dynamics in asymptomatic patients with COVID-19. International Journal of Infectious Diseases 96, 288-290 (2020).

  25. Reintjes, R. Lessons in contact tracing from Germany. BMJ 369, m2522, doi:10.1136/bmj.m2522 (2020).

  26. Chu, D. K. et al. Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis. The Lancet 395, 1973-1987 (2020).

  27. Horby, P. et al. Effect of Dexamethasone in Hospitalized Patients with COVID-19: Preliminary Report. medRxiv, 2020.2006.2022.20137273 (2020).

  28. Imperial College COVID-19 response team. Report 16: Role of testing in COVID-19 control. (2020). https://www.imperial.ac.uk/mrc-global-infectious-disease-analysis/covid-19/report-16-testing/.

  29. Stein-Zamir, C. et al. A large COVID-19 outbreak in a high school 10 days after schools’ reopening, Israel, May 2020. Eurosurveillance 25, 2001352, doi:doi:https://doi.org/10.2807/1560-7917.ES.2020.25.29.2001352 (2020).