How diseases affect symbiotic communities

Examples of species living in symbiotic communities are well known among biologists. In this study we extend our previous analysis of predator–prey or competing models subject to a disease spreading among one of the species to populations mutually benefiting from interactions. We assume that one of the species is subject to a disease which cannot cross the species barrier and investigate the behavior of such a community. Our findings indicate that there are parameter ranges for which an interesting phenomenon occurs. Namely, the equilibrium shifts to a higher value. That is, the disease seems to have a positive effect on the environment as also field experiments show.