The methodology for this application comes from our paper which is currently under peer review and is available on medRxiv.

In short, we use a compartmental model with compartments for susceptible, infections - asymptomatic, infectious - symptomatic, and removed. We assume mixing happens over 8 hours of a 24 hour day and that infections are seeded within the community being tested as well as by the external community.

Test Details

Estimates for cost, accuracy, and speed by type of COVID-19 test used in the simple dashboard are as follows.

Test Type
Speed of Results
Pooling Possible
4 days
PCR rapid turnaround
<3 hours
<1 hour
<1 hour

Note that numbers and ranges are approximate and not linked to any specific test or test manufacturer. To investigate how different ranges affect outcomes, see the detailed calculator.

Most EUA's are for symptomatic patients and a small sample size. These numbers may change as more information about performance in practice becomes available.

Testing Strategy and Disease Parameters

  • $\boldsymbol{R_0}$: Number of cases generated by one case when no other individuals in the population are infected or immune. The scientific community has not yet reached consensus on the $ R_0 $ value for COVID-19, but a median value of $R_0$ that can be used for this COVID-19 testing projection is 2.5.
  • Average number of infectious days: Debate surrounds this number, as well. A median value that can be used for this COVID-19 testing projection is 9 days. See references here, here, here, and here. An additional resource explaining disease progression is available in the article Charting a Coronavirus Infection

Community Prevalence

To account for the introduction of infections from the surrounding community, we added a time-dependent term that represents the rate (in people/time) of infections from outside interactions. With frequent testing, this external forcing drives the behavior of the model.

We examine three scenarios for this external forcing. We took all case counts from the New York Times on September 23, 2020 and considered all counties with at least 30 deaths reported by September 23, 2020. We then considered a seven day rolling average of the most recent 100 days and found counties whose average number of new cases, per person, per day were representative of the 25th, 50th, and 75th percentile. The represenative counties chosen were (low) Winnebago County, Illinois, (medium) Pottawattamie County, Iowa, and (high) Harris County, Texas.


We encourage suggestions of new features and improvements to make the visualizations more helpful.

Send questions for the authors, questions about the calculator or its code, and media requests to


  1. Service RF. Coronavirus antigen tests: quick and cheap, but too often wrong? Science | AAAS. Published May 22, 2020. Accessed September 23, 2020.

  2. Corman VM, Rabenau HF, Adams O, et al. SARS-CoV-2 asymptomatic and symptomatic patients and risk for transfusion transmission. Transfusion. 2020;60(6):1119-1122. doi:10.1111/trf.15841

  3. FDA. Emergency Use Authorization. FDA. Published online September 22, 2020. Accessed September 23, 2020.

  4. Abdalhamid B, Bilder CR, McCutchen EL, Hinrichs SH, Koepsell SA, Iwen PC. Assessment of Specimen Pooling to Conserve SARS CoV-2 Testing Resources. Am J Clin Pathol. Published online April 18, 2020. doi:10.1093/ajcp/aqaa064

  5. The New York Times. NYT COVID-19 Data. COVID-19 Data. Published September 23, 2020. Accessed September 23, 2020.

  6. Smith, David RM, Duval, Audrey, Pouwels, Koen B, et al. Optimizing COVID-19 surveillance in long-term care facilities: a modelling study. Published online August 13, 2020.

  7. Watkins AE, Fenichel EP, Weinberger DM, et al. Pooling Saliva to Increase SARS-CoV-2 Testing Capacity. Infectious Diseases (except HIV/AIDS); 2020. doi:10.1101/2020.09.02.20183830

  8. Wu JT, Leung K, Leung GM. Nowcasting and forecasting the potential domestic and international spread of the 2019-nCoV outbreak originating in Wuhan, China: a modelling study. The Lancet. 2020;395(10225):689-697. doi:10.1016/S0140-6736(20)30260-9

  9. Bezanson J, Edelman A, Karpinski S, Shah VB. Julia: A Fresh Approach to Numerical Computing. SIAM Rev. 2017;59(1):65-98. doi:10.1137/141000671

  10. Health C for D and R. SARS-CoV-2 Reference Panel Comparative Data. FDA. Published online September 15, 2020. Accessed September 25, 2020.

  11. Bilder CR. Group Testing for Identification. In: Wiley StatsRef: Statistics Reference Online. American Cancer Society; 2019:1-11. doi:10.1002/9781118445112.stat08227

  12. Chan CL, Jaggi S, Saligrama V, Agnihotri S. Non-Adaptive Group Testing: Explicit Bounds and Novel Algorithms. IEEE Transactions on Information Theory. 2014;60(5):3019-3035. doi:10.1109/TIT.2014.2310477

  13. Paltiel AD, Zheng A, Walensky RP. Assessment of SARS-CoV-2 Screening Strategies to Permit the Safe Reopening of College Campuses in the United States. JAMA Netw Open. 2020;3(7):e2016818-e2016818. doi:10.1001/jamanetworkopen.2020.16818

  14. Larremore DB, Wilder, Bryan, Lester, Evan, et al. Test sensitivity is secondary to frequency and turnaround time for COVID-19 surveillance.

  15. Bullard J, Dust K, Funk D, et al. Predicting Infectious Severe Acute Respiratory Syndrome Coronavirus 2 From Diagnostic Samples. Clin Infect Dis. doi:10.1093/cid/ciaa638

  16. He D, Zhao S, Lin Q, et al. The relative transmissibility of asymptomatic COVID-19 infections among close contacts. International Journal of Infectious Diseases. 2020;94:145-147. doi:10.1016/j.ijid.2020.04.034

  17. Huang C-G, Lee K-M, Hsiao M-J, et al. Culture-Based Virus Isolation To Evaluate Potential Infectivity of Clinical Specimens Tested for COVID-19. Journal of Clinical Microbiology. 2020;58(8). doi:10.1128/JCM.01068-20

  18. Perera RAPM, Tso E, Tsang OTY, et al. SARS-CoV-2 Virus Culture and Subgenomic RNA for Respiratory Specimens from Patients with Mild Coronavirus Disease. Emerging Infectious Diseases. 26(11). doi:10.3201/eid2611.203219

  19. Singanayagam A, Patel M, Charlett A, et al. Duration of infectiousness and correlation with RT-PCR cycle threshold values in cases of COVID-19, England, January to May 2020. Eurosurveillance. 2020;25(32):2001483. doi:10.2807/1560-7917.ES.2020.25.32.2001483

  20. Ferretti L, Ledda A, Wymant C, et al. The timing of COVID-19 transmission. medRxiv. Published online September 16, 2020:2020.09.04.20188516. doi:10.1101/2020.09.04.20188516

  21. Mizumoto K, Kagaya K, Zarebski A, Chowell G. Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020. Eurosurveillance. 2020;25(10):2000180. doi:10.2807/1560-7917.ES.2020.25.10.2000180

  22. Savvides, Christina, Siegel, Robert. Asymptomatic and presymptomatic transmission of SARS-CoV-2: A systematic review.

  23. Zhen W, Manji R, Smith E, Berry GJ. Comparison of Four Molecular In Vitro Diagnostic Assays for the Detection of SARS-CoV-2 in Nasopharyngeal Specimens. Journal of Clinical Microbiology. 2020;58(8). doi:10.1128/JCM.00743-20

  24. Kirkcaldy RD, King BA, Brooks JT. COVID-19 and Postinfection Immunity: Limited Evidence, Many Remaining Questions. JAMA. 2020;323(22):2245-2246. doi:10.1001/jama.2020.7869

  25. Xing Y, Mo P, Xiao Y, Zhao O, Zhang Y, Wang F. Post-discharge surveillance and positive virus detection in two medical staff recovered from coronavirus disease 2019 (COVID-19), China, January to February 2020. Eurosurveillance. 2020;25(10):2000191. doi:10.2807/1560-7917.ES.2020.25.10.2000191

  26. Bao L, Deng W, Gao H, et al. Lack of Reinfection in Rhesus Macaques Infected with SARS-CoV-2. bioRxiv. Published online May 1, 2020:2020.03.13.990226. doi:10.1101/2020.03.13.990226

  27. Xiao AT, Tong YX, Zhang S. False negative of RT-PCR and prolonged nucleic acid conversion in COVID-19: Rather than recurrence. Journal of Medical Virology. 2020;92(10):1755-1756. doi:10.1002/jmv.25855

  28. Lan L, Xu D, Ye G, et al. Positive RT-PCR Test Results in Patients Recovered From COVID-19. JAMA. 2020;323(15):1502-1503. doi:10.1001/jama.2020.278

  29. Wu J, Liu X, Liu J, et al. Coronavirus Disease 2019 Test Results After Clinical Recovery and Hospital Discharge Among Patients in China. JAMA network open. 2020;3(5):e209759. doi:10.1001/jamanetworkopen.2020.9759

  30. Watkins AE, Fenichel EP, Weinberger DM, et al. Pooling saliva to increase SARS-CoV-2 testing capacity. medRxiv. Published online September 3, 2020:2020.09.02.20183830. doi:10.1101/2020.09.02.20183830