Figure 1. . . . . Madagascar (gray shading in inset), showing the main roads, the capital of Antananarivo (square), the harbor city of Toamasina (white circle), and the locations of the 6 study sites (black circles) from which serologic samples from pregnant women were screened for IgG against chikungunya virus, dengue virus, and Rift Valley fever virus. The altitudes of the locations are as follows: Mananjary and Manakar, coastal; Ifanadiana, 466 m; Moramanga, 920 m; Tsiroanomandidy, 860 m; Ambositra, 1,280 m; Toamasina, coastal; Irondro, 40 m; Antananarivo, 1,300 m.