Distribution of viraemia levels in: (A) patients with primary and secondary dengue infections; (B) patients with primary and secondary dengue infection and fever history; (C) patients with DENV-1, DENV-2, DENV-3 and DENV-4 infections; (D) patients with and without NS1 antigen. All comparison within groups was performed using Mann–Whitney tests. Box plots show median values (horizontal line in the box), 25–75% interquartile range (lower-upper limits of the box), 90% range of data (additional bars), and outliers (circles).