The <SEIR model> inserts a latent exposed state:
$$
S\xrightarrow{\lambda(t)}E\xrightarrow{\sigma}I\xrightarrow{\gamma}R.
$$
The expected time from infection through the end of infectiousness is $d=1/\sigma+1/\gamma$; the duration during which transmission occurs is $1/\gamma$.

Solution

Past exam of the mathematics course of the University of Cambridge / 2025 / iii / Paper 207 / 2 / d / ii / Solution

 Solution

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