in figure 1) is therefore described by the following differential equations:
Susceptible Sg  (1a)  d S g    d t   =  − λ g   S g
Exposed Eg  (1b)  d E g    d t   =  λ g   S g   − η E g
Asymptomatic Ag  (1c)  d A g    d t   = η ( 1 − δ  )  E g   − μ A g
Infectious Ig  (1d)  d I g    d t   = η δ E g   − μ I g
Hospitalised in acute bed Hg  (1e)  d H g    d t   = μ γ g   I g   −