Low Zika virus seroprevalence in Vientiane, Laos, 2003-2015 per Pastorino, B, Sengvilaipaseuth, O, Chanthongthip, A, Vongsouvath, M, Souksakhone, C, Mayxay, M, Thirion, L, Newton, P, De Lamballerie, X, Dubot-Pérès, A