As an in vitro study of promoter activity might not reflect an actual functional association, we aimed to test whether the rs4804803 SNP in the promoter region of CD209 was associated with the susceptibility to DF and/or DHF in Taiwanese, and whether monocyte-derived DCs from humans with various genotypes of rs4804803 would reveal differences in DC-SIGN membrane expression and implicate the viral replication and immune reactions after DEN infection. The gene discussed is CD209; the disease is Dengue hemorrhagic fever.