Estimation of the Severeness Rate, Death Rate, Household Attack Rate and the Total Number of COVID-19 Cases Based on 16115 Polish Surveillance Records

BackgroundEstimating the actual number of COVID-19 infections is crucial for steering through the COVID-19 pandemic crisis. It is, however, notoriously difficult, as many cases have no or only mild symptoms. Surveillance data for in-household secondary infections offers unbiased samples for COVID-19 prevalence estimation.MethodsWe analyse 16 115 Polish surveillance records to obtain key figures of the COVID-19 pandemic. We propose conservative upper and lower bound estimators for the number of SARS-CoV-2 infections. Further, we estimate age-dependent bounds on the severe case rate, death rate, and the in-household attack rate.ResultsBy maximum likelihood estimates, the total number of COVID-19 cases in Poland as of July 22nd, 2020, is at most around 13 times larger and at least 1.6 times larger than the recorded number. The lower bound on the severeness rate ranges between 0.2% for the 0–39 year-old to 5.7% for older than 80, while the upper bound is between 2.6% and 34.1%. The lower bound on the death rate is between 0.04% for the age group 40–59 to 1.34% for the oldest. Overall, the severeness and death rates grow exponentially with age. The in-household attack ratio is 8.18% for the youngest group and 16.88% for the oldest.ConclusionsThe proposed approach derives highly relevant figures on the COVID-19 pandemic from routine surveillance data, under assumption that household members of detected infected are tested and all severe cases are diagnosed.MOCOSThe MOCOS (MOdellingCOronaSpread) international research group is an interdisciplinary scientific consortium. The following authors are MOCOS members: Barbara Adamik, Marek Bawiec, Viktor Bezborodov, Przemyslaw Biecek, Wolfgang Bock, Marcin Bodych, Jan Pablo Burgard, Tyll Krueger, Agata Migalska, Tomasz Ożański, Barbara Pabjan, Magdalena Rosińska, Piotr Sobczyk and Ewa Szczurek