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

Tracking the spread of epidemics requires accurate case reporting and strong international collaboration. Failure to do so leaves us vulnerable to surveillance 'blind spots', with the potential for prolonging epidemics and increasing their geographic spread. Zika virus was first detected in Brazil in May, 2015 (Zanluca et al., 2015) , yet studies have shown that the epidemic started at least one and a half years prior to its discovery (Faria et al., 2017) . Early in 2016, 48 countries across the Americas reported local outbreaks (PAHO, 2017b), with case numbers peaking later that year. By mid 2017, new Zika cases were no longer being reported to the international community (PAHO, 2017b). Due to widespread surveillance gaps and inconsistent reporting, however, we hypothesized that local Zika outbreaks could still be occurring in the Americas, despite not being captured by the international community. To investigate whether Zika virus transmission is still ongoing, we used international travel data to reveal that local outbreaks were still occurring in 2017, despite relatively few cases being reported (Fig. 1) . Our data demonstrate that the vast majority of Zika cases during 2017 were the result of an unreported Zika outbreak in Cuba, which occurred while public data suggested the epidemic was nearing its end in the Americas (PAHO, 2017a) (Fig. 1) .