Fig. 1.

(A) The test sensitivity as a function of time from Hellewell et al. (2021). The function, $S\left(\tau \right)$ gives the probability that a PCR test will be positive if performed on an infected person $\tau$ days after exposure. (B) The incubation period probability distribution from Lauer et al. (2020), shown here are the probability of symptom onset on each day since exposure.