Figure 1.

The reporting pyramid of COVID-19. The base holds all infections with COVID-19 in the population, both symptomatic and asymptomatic. This base contributes to the SARS-CoV-2 discharged into the sewerage network. Moving upwards the numbers shrink, since not everybody with an infection is symptomatic, and not every symptomatic individual gets tested and there may be some delay or loss of reporting the local test data to national public health agencies. Ascending further, the numbers shrink by the nature of COVID-19: only a fraction of the reported COVID-19 cases end up in hospital, IC or die as a result of the disease.