To investigate the prevalence of blood donors with recently asymptomatic DENV infection, we conducted a retrospective study to detect the presence of the DENV RNA genome, NS1 antigen and anti-dengue IgM/IgG in bloods that were donated to the blood centers of the TBSF in Kaohsiung City and Tainan City during the largest dengue outbreak in Taiwan history in 2015. The gene discussed is CD40LG; the disease is dengue disease.