Figure 3.

Age distribution of seroprevalence of Zika virus infection. The shaded area represents the interquartile range for maternal age in Brazil, the origin of the current outbreak of Zika virus. Age intervals: narrower intervals report on individuals aged 0–4, 5–9, 10–14, 15–19, 20–29, 30–39 and ≥40 years; wider intervals report on individuals aged 0–9, 10–19, 20–29, 30–39 and ≥40 years; and dual age intervals with a cut-point at 13^{46 71} or 15 years,^{43 66 67 73 76 77 82 87 91 93 100 104} compare children to adults. Data were reported in the narrower intervals for 16 223 individuals tested in Cameroon, Central African Republic, Côte d'Ivoire, Kenya, Nigeria, Philippines, Senegal and Uganda,^{22 37 44 45 62 63 72 73 76 81 84 86 92} in the wider intervals for 874 individuals in Central African Republic,^{40 97} and in dual intervals for 13 892 individuals in all 20 countries where seroprevalence by age was reported. Methods: Bézier spline smoothed scatterplot with point data for age intervals placed at the upper bound of each interval. Point data from studies comparing children to adults were placed at 15 and 39 years, and the line was then projected under an assumption of constant slope. The IQR for maternal age in Brazil was estimated by indirect standardisation using 2010 age-specific fertility rates and female population by age in Brazil.^{105 106}