The observation that the emergence #drug_resistant_malaria is more common in Southeast Asia than in #Africa, which has the highest #prevalence_of_malaria in the world, has long puzzled researchers. Now, computer modelling suggests that this finding might be partially explained by the competition between various strains of malaria in the bloodstream of the host (#within_host_competition).

Multiple strains of the malarial parasite (#Plasmodium_falciparum) generally infect a single individual. Computer modelling suggests that in conditions where incidence of malaria is high, the drug-sensitive strains of malaria rapidly outcompete the resistant strains. However, if the incidence of malaria is low, the likelihood of drug-resistant strains gaining a foothold is high.

Computer modelling also suggested that the use of #anti_malarial_drugs quickly eliminates the drug-sensitive strains of the #parasite in areas with a high #disease_burden and having a significant number of resistant strains, resulting in the widespread diffusion of resistant strains.

Thus, drug-resistant strains face a higher risk of extermination in a “high-transmission-setting” like Africa than in a “low-transmission-setting” like Southeast Asia. However, when drug-resistant strains of malaria do manage to avoid elimination, their subsequent spread might be more rapid in high-transmission-settings than in low-transmission-settings, especially under high #selection_pressure.

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