Using random testing to manage a safe exit from the COVID-19 lockdown

Markus Mueller; Peter Derlet; Christopher Mudry; Gabriel Aeppli

We argue that the moderate number of 15'000 random tests per day yields valuable information on the dynamics of the disease. Assuming that at a given time a conservatively estimated fraction of about i * ≈ 0.07% of the population is currently infected [see Eq. 15d], on the order of 10 infected people will be detected every day. Can such a small number of detected infections be useful at all, given that these numbers fluctuate significantly from day to day? The answer is yes. We show that after a few days the acquired signal becomes stronger than the noise level. It is then possible to establish whether the infection number is growing or decreasing and, moreover, to obtain a quantitative estimate of the instantaneous growth rate k(t).