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

Though we previously hypothesized cruise ships may have an underrecognized role in Zika virus spread , we did not use data from Zika virus infections that may have been associated with cruise travel, and thus did not collect cruise ship data for this study. First, there were very few infections linked to cruise travel in our dataset, which may be because these cases would more likely be tourists diagnosed elsewhere (and just visiting Florida for the cruise departure). Second, many of the reported cruise-related Zika infections were associated with more than one site for potential exposure, making it difficult to estimate local incidence rates (we removed all travel cases with multiple locations of potential exposure from our analyses). Third, scheduled cruise ship passengers arriving in Florida that stopped in Cuba are predicted to be substantially fewer (11,675/month scheduled for 2019; crawled from CruiseMapper: https://www.cruisemapper.com/) than air travel passengers from Cuba to Florida (80,366/month in 2017) . Cruise travel between Cuba and Florida only began in 2016 (Vora, 2016) , and thus there would have been even fewer passengers during our primary study period between 2016-2017.