title: The dynamics of simultaneous infections with altered susceptibilities.
abstract: We describe a model in which individuals can be infected simultaneously by multiple diseases or parasites, taking into account the fact that individuals already infected by a subset of n co-circulating diseases may see their susceptibility to concurrent infection by another disease from the pool either enhanced or reduced. We propose an n-dimensional approximation to the 2n dimensional model required to describe the dynamics of each possible subset of the pool of n co-circulating diseases, using as state variables the overall prevalence of each infection. Analysis of the two disease case shows that the reduced model provides a very good approximation throughout the full dynamics for small alterations of susceptibility, and, after a transient error, a good approximation to the complete model when susceptibilities are highly enhanced. As the number of diseases becomes large, the approximation remains close for small alterations of susceptibility.
authors.affiliation: Center for Applied Mathematics, Cornell University, Ithaca, New York 14853.
authors.forename: F R
authors.initials: FR
authors.lastname: Adler
authors.forename: R C
authors.initials: RC
authors.lastname: Brunet
mesh_terms: D015897:Comorbidity; D004198:Disease Susceptibility / Q000453:epidemiology*; D006801:Humans; D007239:Infections / Q000453:epidemiology*; D008433:Mathematics; D008954:Models, Biological