Antibody responses to different ZIKV or DENV proteins. Preinfection sera from ZIKV (A) or DENV (B) IgM-positive subjects were subjected to Western blot analysis using lysates derived from African ZIKV (unpublished strain)- or DENV2 (NGC strain)-infected Vero cells. (C) FL0232, a mouse anti-E monoclonal antibody recognizing similar flaviviral E protein levels, was used to standardize comparable amounts of E proteins from different virus-infected Vero cell lysates. (D) sD-ID27 is a confirmed case of secondary DENV1 infection at 3 months postinfection run on DENV1-4 Vero cell lysates. (E) Dak010 is a confirmed case of African ZIKV infection run on an African ZIKV Vero cell lysate. Arrowheads indicate PrM, E, and NS1 proteins recognized. Molecular size marker units are kilodaltons. Mo, mock-infected; m, molecular mass marker; D1, DENV1; D2, DENV2; D3, DENV3; D4, DENV4; ZV, ZIKV.