Fig. 1
Model schematic of the SARS-CoV-2 infection and disease process in residents and staff. Residents were classified into susceptible (Sr), exposed (Er), infectious asymptomatic (Ia,r), infectious preclinical (Ipc,r), infectious clinical with high infectiousness (Ich,r), infectious clinical with low infectiousness (Icl,r), and recovered (Rr) compartments. Staff were classified into susceptible (Ss), exposed (Es), infectious asymptomatic (Ia,s), infectious preclinical (Ipc,s), infectious clinical with high infectiousness (Ich,s), and recovered (Rs) compartments. Darker shades denote compartments that contribute towards the force of infection. Resident movements are denoted by bold purple arrows, staff movements are denoted by bold green arrows and visiting is denoted by a bold orange arrow. Residents exit the care home due to hospital visits for COVID-19 and non-COVID-19 reasons or as a result of death. Residents enter the care home from the hospital following a COVID-19 admission, a non-COVID-19 admission or as a new admission. Within-hospital transmission dynamics were not modelled explicitly. Flows of new care home residents arriving from the community and care home residents moving into the community are assumed to be negligible during the pandemic and thus are not considered in the model. Staff are assumed to live in the community, and a small proportion of staff work at another care home. Staff may become absent because of COVID-19 symptoms or a positive test, and return to the care home recovered. Absent staff may be replaced by a secondary pool of staff, who in turn leave the care home as the original staff return from their absence