Basic estimation-prediction techniques for Covid-19, and a prediction for Stockholm

Tom Britton

fatalities was around d = 3.5 days before preventive measures were put in place [7] , and we assume that R 0 = 2.5 this being a common estimate [9] . A number of (mainly but not exclusively) preventive measures were put in place around the date t p = March 16. We assume the typical time between infection and death (for those who die from covid-19) equals s D = 21 days. These preventive measures will start affecting fatality rates at t p + s D = April 6. We are now (April 14) one week later so the effect is still very (!) uncertain, but d E = 9 days seems to be a reasonable estimate based (only) on case fatalities between April 4 and April 13 where the total number has close to doubled [7] . To calibrate the relative time to calendar time we finally assume that the cumulative number of case fatalities on March 31, before effect of preventive measures, equals Λ(March 31) = 200. We emphasize that the quantities are by no means precisely estimated, so results contain a lot of uncertainty.