0 -> Susceptible
Exposed -> Susceptible
Susceptible -> Exposed
Susceptible -> 0
Exposed -> 0
Exposed -> Infected_Symptomatic
Exposed -> Infected_Asymptomatic
Infected_Symptomatic -> 0
Infected_Asymptomatic -> 0
Infected_Symptomatic -> Recovered
Infected_Asymptomatic -> Recovered
Recovered -> 0
0 -> Pathogen_0
Pathogen_0 -> 0