RESEARCH ARTICLE Multiplicity of Infection and Disease Severity in Plasmodium vivax

Background Multiplicity of infection (MOI) refers to the average number of distinct parasite genotypes concurrently infecting a patient. Although several studies have reported on MOI and the fre-quency of multiclonal infections in Plasmodium falciparum, there is limited data on Plasmo-dium vivax. Here, MOI and the frequency of multiclonal infections were studied in areas from South America where P. vivax and P. falciparum can be compared. Methodology/Principal Findings As part of a passive surveillance study, 1,328 positive malaria patients were recruited between 2011 and 2013 in low transmission areas from Colombia. Of those, there were only 38 P. vivax and 24 P. falciparum clinically complicated cases scattered throughout the time of the study. Samples from uncomplicated cases were matched in time and location with the complicated cases in order to compare the circulating genotypes for these two cate-gories. A total of 92 P. vivax and 57 P. falciparum uncomplicated cases were randomly sub-sampled. All samples were genotyped by using neutral microsatellites. Plasmodium viva