A total of 32 anonymised sera, obtained from symptomatic patients with COVID-19 diagnosed by positive anti-SARS-CoV-2 IgM/IgG (32/32, tested by 2019-NCOV IgG/IgM Rapid Test Cassette, ScreenItalia, Perugia, Italy) and/or RT-PCR for SARS-CoV-2 on nasopharyngeal swab (26/32), were tested by Dengue Enzyme Linked Immune Assay (ELISA) DENV IgG-IgM (VIRCELL, Granada, Spain). This evidence concerns the gene CD40LG and COVID-19.