Considering early illness (days 1–3) compared to follow-up (day >13), dengue patients had lower l-arginine levels (P < .001) (Supplementary Figure 1A) and l-arginine-to-ADMA ratio (P < .001), and higher arginase-1 levels (P = .004) (Supplementary Figure 2A). Here, ARG1 is linked to dengue disease.