Plasma concentrations of syndecan-1 were correlated with duration of fever in knowlesi malaria (r = 0.30, p < 0.0001) and in vivax malaria (r = 0.49, p < 0.001); in both species this remained significant after controlling for parasitemia (knowlesi malaria: p < 0.001; vivax malaria: p = 0.020). Here, SDC1 is linked to Plasmodium vivax malaria.