Basic prediction methodology for covid-19: estimation and sensitivity considerations

Tom Britton

If R 0 = 3 and the doubling time equals d = 3 corresponding to an exponential growth rate of r = ln(2)/3 = 0.23. If the magnitude of the overall effect of preventive measures equals ρ = 1/3, then using relation (1) gives a mean generation time g 1 = (R 0 − 1)/r = 8.7 days. The new exponential growth rate after preventive measure are put in place hence equals r (1) E = (R E − 1)/g 1 = 0.11. If instead relation (2) is used, the mean generation time is g 2 = ln(R 0 )/r = 4.5 days. As a consequence, the new exponential growth rate assuming relation (2) equals r (2) E = ln(R E )/g 2 = 0.14. From the two bounds we hence conclude that r E should satisfy 0.11 ≤ r E ≤ 0.14.