Speaker
Description
Following the Zika virus (ZIKV) epidemic in the Americas, 1,089 travel-related ZIKV cases occurred in Florida between 2016-2017, together with 276 locally acquired cases in 2016. We used epidemiological data collected in Florida during 2015-2017 to develop new models to infer temporality of importation and local transmission.
We sequenced 25 ZIKV genomes from locally acquired and 38 travel-related cases and identified transmission clades with IQ-TREE adding 575 ZIKV publicly available genomes, including 49 from Florida. We inferred phylogeographic transmission in BEAST. Using epidemiological investigation as a gold standard, we determined the accuracy of models to classify cases as locally or travel-acquired. Posterior probabilities from phylogeographic analysis, sample collection time, vector abundance, travel volumes by cruise and air, and ZIKV prevalence were used as predictors in regression models.
Five clades identified multi-country independent introductions of ZIKV in Florida. Highest likelihood of importation and local transmission were estimated to be between January and April from Brazil, April to May from Colombia, April to August from Dominican Republic and Honduras, in April and July from Suriname, Guadalupe, Guatemala, Jamaica, Mexico, and Nicaragua, and in October from Puerto Rico. Regression models predicted importation status with an accuracy of 93% using phylogeography-inferred origin country and time of sequence sampling.
Multiple ZIKV introductions occurred at several points in time that led to local transmission foci in urban Florida settings. Time to the most common ancestor of locally acquired cases was months before the first reported local transmission suggesting undetected transmission and highlighting the need for prediction models that allow early detection and interventions. Our likelihood model infers countries as source of ZIKV importations in Florida and the temporality for local transmission in Florida. We plan to expand the current models to predict effect of change in climatic condition on risk of arboviral importation and local transmission.
