Fig. 1
From: Design of effective outpatient sentinel surveillance for COVID-19 decision-making: a modeling study
The model framework used in this study. (A) SEIR model structure to simulate SARS-CoV-2 transmission. S = Susceptible, E = Exposed, A = Asymptomatic, P = Presymptomatic, Sm = Mild symptomatic, Ss = Severe symptomatic, H = Requires hospitalization, C = Critically ill (ICU), Hp = Hospitalization post-ICU, D = Death, R = Recovered. All severely symptomatic persons were isolated (SSi) a few days after entering the state and become less infectious. (B) Simulated transmission rate begins low and steady, then experiences a step increase (transmission hike) at 3 possible magnitudes to create different strengths of epidemic waves. When the surveillance indicator reaches a predetermined threshold, mitigative actions are triggered in the simulation and the transmission rate is decreased to its baseline rate