Fig. 6.

Observability of $\kappa$ (latent period) in SEIR models. Models in which $\kappa$ is observable are shown in green, and non-observable in red. Models in which it is unobservable if constant and observable if time-varying are shown in a green–red gradient. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)