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

By sequencing Zika virus genomes from travelers infected in Cuba, we demonstrate that the 2017 outbreak was sparked by at least three introductions of the virus a year earlier (Fig. 3) . Given our estimated size of the outbreak in Cuba, however, there are likely many additional Zika virus introductions not captured in our analyses . Our tMRCA estimates of the Zika virus lineages from Cuba suggest that the virus survived the low mosquito abundance season (i.e. 'overwintered' from November to March) to cause more intense transmission in 2017 after the local mosquito population rebounded. While the factors supporting virus 'overwintering' are still unclear, it is plausible that Zika virus may have survived low mosquito abundance through a combination of low level mosquito-to-human transmission, vertical transmission in mosquitoes (da Costa et al., 2018; Thangamani et al., 2016) , and, to a lesser extend, human sexual transmission (Althaus and Low, 2016). Considering that a large Zika outbreak in Cuba did not occur until after the viruses successfully 'overwintered', which may happen often with Zika outbreaks (Faria et al., 2017; Thézé et al., 2018) , better understanding of how Zika virus is maintained when mosquito abundance is low might lead to novel control methods.