Figure 4. A combined model for the transmission of cholera from the perspective of the host and microorganisms.

The total population (H) feeds the pool of susceptible hosts (S) that become infectious (I) after consuming Vibrio cholerae from an environmental source, with or without lytic bacteriophages (Φ). Infected individuals are symptomatic (I_symp) or asymptomatic (I_asymp) and recover (R) through the actions of their immune systems and possibly those of lytic bacteriophages, or succumb to the infection (m). Recovered individuals will re-enter the susceptible pool at varying rates (//) depending on the degree of protective immunity. Lytic phages and hyperinfectious V. cholerae(VC_Hi) are shed by the symptomatic host in varying concentrations; asymptomatic hosts shed far fewer bacteria (dashed line). VC_Hi cells rapidly passage to the next host, persist in the environment as culturable cells with unknown infectivity (VC_C) or decay into an ‘active but non-culturable’ state (VC_ABNC) with reduced infectivity. All three cell types plus aggregate bacteria (not shown) probably have mixed roles as environmental reservoirs for future outbreaks.