Estimates of the Undetected Rate among the SARS-CoV-2 Infected using Testing Data from Iceland

James H Stock; Karl M Aspelund; Michael Droste; Christopher D Walker

• Population: Statistics Iceland estimates that the population of Iceland was 364,134 on January 1, 2020. 6 • : From the Directorate of Health's counts, we calculate the total count of NUHI infected cases and divide by the total count of NUHI tests from March 13 through March 19, to match the deCODE testing dates. • 0 : We use Directorate of Health weekly influenza count data to estimate λ0 by the greatest one-week fraction of Icelanders reporting flu symptoms. 7 This period occurred in November 2009 during the H1N1 pandemic and was 0.63%. To bound the proportion mildly symptomatic, we use a lower value of λ0 which is the average rate of reported flu symptoms in the two-week period around March 15 from 2011-2018, which is 0.17%. • ( | = 1, = 0, = 0), ( | = 0, = 0, = 0): Under the assumption that deCODE randomly tests within the deCODE-eligible symptomatic and asymptomatic groups, then these terms are estimated by the deCODE positive testing rates within these two groups as reported in Table 1 of Guðbjartsson et al (2020) for deCODE testing from March 13 through March 19.