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An antigenic diversification threshold for falciparum malaria transmission at high endemicity

Fig 3

Numerical simulations reveal a transition between two regimes of antigenic diversity accumulation.

(A) The percentage of new genes in the local parasite population at the end of a given simulation period (200 years) remains negligible when the reproductive number Rdiv for antigen-encoding new genes is lower than one. By contrast, this percentage increases rapidly above this threshold. Because the time interval over which we computed Rdiv = Gnew Tnew concerns long transients, we evaluated the rate of generation of new genes Gnew as a mean over this interval (by averaging the values of N and every 180-day interval), and the lifespan Tnew, as an average for all the new genes that invaded during this time (with this interval placing an upper bound on individual lifespans). (A, B) Each point represents a simulation with different combinations of parameters and assumptions (including variation in rules of within-host dynamics, in strength of the trade-off between transmissibility and duration of infection, and in values and seasonality of the transmission rates, Table A and Table B in S1 Text). (B) The percentage of new genes also exhibits the threshold behavior with the entomological inoculation rate (EIR, the number of infectious bites per person per year).

Fig 3