CD40LG and Zika virus infectious disease: Analyzing the kinetics of passively-acquired flavivirus immunity in young children, we found that ZIKV-reactive IgG decays at an estimated rate of 3.23% and 3.85% decay per week to low or undetectable levels by 6 to 9 months of age, confirming recent findings of Coutinho, et al. that IgG declined independently of anti-ZIKV IgM detection, and similarly in babies with and without known congenital ZIKV infections in Brazilian and Nicaraguan infants [45].