CD40LG and dengue disease: <h4>Background</h4>Co-circulation of Plasmodium vivax and arboviruses is a significant but underexplored public health concern in tropical regions.<h4>Methods</h4>We analyzed 300 serum samples collected between 2014 and 2015 from the Brazil-French Guiana border, including 102 malaria cases and 198 controls, using rapid tests for Immunoglobulin M (IgM), Immunoglobulin G (IgG), and Non-Structural Protein 1 (NS1).<h4>Results</h4>High IgG reactivity for dengue and chikungunya viruses was observed.