Current infection: detection of Zika virus nucleic acid by RT–PCR in any specimen (serum, urine or whole blood).Recent infection: detection of anti-Zika virus IgM antibody by ELISA in serum. Recent flavivirus infection: detection of both anti-Zika virus IgM and anti-dengue virus IgM antibodies by ELISA in a serum specimen, in the absence of Zika virus or dengue virus nucleic acid detection (results were a subset of recent Zika virus infection).Zika virus positivity: evidence of current or recent Zika virus or flavivirus infection. Here, CD40LG is linked to infection.