Fig. 4. Quantitative reactivity of ELISA for anti-Zika virus IgG (A) and high-avidity anti-Zika virus IgG (B) in serum using protein antigen from ultracentrifuged virions in solid support. Sample origin: DM: acute dengue virus infection with positive IgM serology. DG: dengue virus infection with positive IgG serology. YF: Yellow fever vaccination patients. N: negative controls from patients without history of travel to endemic areas. ZKVR: Acute patients with Zika virus with previous RNA detection. MM: Samples after delivery from mothers with microcephaly babies. Interruptions in the axes show the cut-off point of the assays. Serological indices are presented in the table below using RT-PCR-positive patient serum as a reference test.