International travelers and genomics uncover a ‘hidden’ Zika outbreak

Nathan D. Grubaugh; Sharada Saraf; Karthik Gangavarapu; Alexander Watts; Amanda L. Tan; Rachel J. Oidtman; Jason T. Ladner; Glenn Oliveira; Nathaniel L. Matteson; Moritz U.G. Kraemer; Chantal B.F. Vogels; Aaron Hentoff; Deepit Bhatia; Danielle Stanek; Blake Scott; Vanessa Landis; Ian Stryker; Marshall R. Cone; Edgar W. Kopp; Andrew C. Cannons; Lea Heberlein-Larson; Stephen White; Leah D. Gillis; Michael J. Ricciardi; Jaclyn Kwal; Paola K. Lichtenberger; Diogo M. Magnani; David I. Watkins; Gustavo Palacios; Davidson H. Hamer; Lauren M. Gardner; T. Alex Perkins; Guy Baele; Kamran Khan; Andrea Morrison; Sharon Isern; Scott F. Michael; Kristian G. Andersen

To determine whether Zika case reports from international travelers could reveal outbreaks not captured by local case reports, we compared the temporal distribution of local and travel-associated Zika cases from 2016 to 2018 (Fig. 1) . We obtained monthly suspected and confirmed Zika cases reported by individual countries and territories from PAHO. We obtained reports of international travelassociated Zika cases from the Florida Department of Health (FL-DOH) and the European Centre for Disease Prevention and Control (ECDC). We constructed Zika epidemic (epi) curves based on either local or travelassociated cases and found that they were in strong agreement from South America (Pearson r = 0.917 and 0.976 using FL-DOH and ECDC data, respectively) and the Caribbean (Pearson r = 0.828 and 0.856), and to a smaller extent Central America and Mexico (Pearson r = 0.542 and 0.583). For South America and Central America, we also found concordance for when the last local and travel cases were reported in August and September, 2017 (Fig. 1A) .