${\mathit{Z}}_{\mathit{i}}$	vector of indicator i for the latent variable degree of COVID-19 severity (${\mathit{\eta }}_{\mathit{C}}$);
${\mathrm{\Lambda }}_{\mathit{i}}$	matrix of pattern coefficients representing the loading of latent variable (${\mathit{\eta }}_{\mathit{C}}$) on indicator i;
${\mathit{∊}}_{\mathit{i}}$	vector of measurement error terms for indicator i of the latent variable.