Regarding the ascertainment of ZIKV infection, 13 studies tested their cases for both PCR and IgM,[4, 14–18, 21, 25, 26, 28, 30, 31, 33] five only for PCR,[19, 20, 22, 29, 32] and three only for IgM.[23, 24, 27] Based on the CDC ZIKV case definition, more than a half of all GBS cases with this data available had a suspected ZIKV infection (324/570, 57%), which gives a high risk for ascertainment bias within studies and heterogeneity across studies. The gene discussed is CD40LG; the disease is Zika virus infectious disease.