title: An apparent paradox of horizontal and vertical disease transmission.
abstract: The question as to how the ratio of horizontal to vertical transmission depends on the coefficient of horizontal transmission is investigated in host-parasite models with one or two parasite strains. In an apparent paradox, this ratio decreases as the coefficient is increased provided that the ratio is taken at the equilibrium at which both host and parasite persist. Moreover, a completely vertically transmitted parasite strain that would go extinct on its own can coexist with a more harmful horizontally transmitted strain by protecting the host against it.
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA.
authors.forename: Stanley H
authors.initials: SH
authors.lastname: Faeth
authors.forename: Karl P
authors.initials: KP
authors.lastname: Hadeler
authors.forename: Horst R
authors.initials: HR
authors.lastname: Thieme
mesh_terms: D000818:Animals; D018562:Disease Transmission, Infectious / Q000706:statistics & numerical data*; D006790:Host-Parasite Interactions; D006801:Humans; D018445:Infectious Disease Transmission, Vertical / Q000706:statistics & numerical data*; D008954:Models, Biological