Figure 1: Summary of the model structure used to represent coronavirus disease 2019 transmission and control in Indian cities. The population in each metropolitan area is divided into different compartments, representing states of disease, with flows between compartments given by the rates shown in the diagram. Thus, susceptible individuals (S), upon acquiring infection, enter a state of asymptomatic infection (E) and with some delay develop symptomatic disease (I). It is assumed that a proportion p of symptomatic cases is subject to quarantine [I(q)] and the remainder [I(n)] is not. The relative size of these two populations (p) reflects the coverage of quarantine efforts. Individuals in I(q) are quarantined with an average quarantine delay (1/δ). Finally, individuals may be cured (R) or die as per recovery rate (γ) or mortality rate (μ), respectively. Those people who are successfully quarantined (Q) do not contribute to onward infection.