Natural history of influenza. After acquiring the infection, a susceptible individual enters the latent compartment, where he is infected but not yet infectious. After the average latency period, each infected individual becomes infectious, and may or may not show symptoms. Symptomatic cases are more infectious than asymptomatic cases. Finally, all infected individuals recover after the average infectious period and become immune to the disease.
Tizzoni et al. BMC Medicine 2012 10:165 doi:10.1186/1741-7015-10-165