In the case of a patient with primary Zika virus infection with no history of other flavivirus infection or vaccination, IgM antibody-capture ELISA was unexpectedly specific for Zika virus with no cross-reaction with other flaviviruses43 (I Leparc-Goffart, French National Reference Centre for Arbovirus, unpublished data, 2016). Here, CD40LG is linked to Zika virus infectious disease.