Figure 1. Compartments and transmission routes.

The upper part of the figure models the flow of individual compartments. The transfer rate from susceptible (S) to infected (I) is the product of the pathogen amount on hands of susceptible (E_HS), the fraction of pathogens E_HS transferred to mucus of susceptible via inoculation (ρ_inoc) and the probability that a susceptible individual becomes infectious per pathogen. The recover rate of infected is γ per unit time. The lower part of the figure models the flow of pathogens. α is the shedding rate per unit time per individual. φ_H proportion of virus goes directly to the hands of an infected individual. The proportion of virus that is excreted to hands and then is associated with a type of fomite is ξ. λ is the fraction of pathogens going to surfaces reach one type of fomite. ρ_F is the individual pick up rate of pathogens on a fomite per unit time and δ is the deposit rate of pathogens from hands to fomites per unit time. µ _H and µ _F are virus inactivation rate on hands and fomites respectively.