Estimating the subcritical transmissibility of the Zika outbreak in the State of Florida, USA, 2016

Dinh, Linh; Chowell, Gerardo; Mizumoto, Kenji; Nishiura, Hiroshi

doi:10.1186/s12976-016-0046-1

Cited by 37 publications

(23 citation statements)

References 12 publications

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“…Given that the majority of ZIKV infections are asymptomatic 2,28 , the true number of ZIKV cases was likely much higher. Despite this, we estimated that the average R 0 was less than 1 and therefore multiple introductions were necessary to give rise to the magnitude of the observed outbreak 25 . The high volume of airline and cruise ship traffic entering Florida from ZIKV-affected regions, especially the Caribbean, likely provided a substantial supply of ZIKV-infected individuals 29,30 .…”

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confidence: 91%

“…The high volume of airline and cruise ship traffic entering Florida from ZIKV-affected regions, especially the Caribbean, likely provided a substantial supply of ZIKV-infected individuals 29,30 . Because Florida is unlikely to sustain long-term ZIKV transmission 25 , the potential for future ZIKV outbreaks in this region is highly dependent upon activity elsewhere. Therefore, we expect that outbreaks in Florida will cycle with the ZIKV transmission dynamics in the Americas 12 .…”

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confidence: 99%

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Multiple introductions of Zika virus into the United States revealed through genomic epidemiology

Grubaugh

Ladner

Kraemer

et al. 2017

Preprint

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Zika virus (ZIKV) is causing an unprecedented epidemic linked to severe congenital syndromes 1,2 . In July 2016, mosquito-borne ZIKV transmission was first reported in the continental United States and since then, hundreds of locally-acquired infections have been reported in Florida 3 . To gain insights into the timing, source, and likely route(s) of introduction of ZIKV into the continental United States, we tracked the virus from its first detection in Miami, Florida by direct sequencing of ZIKV genomes from infected patients and Aedes aegypti mosquitoes. We show that at least four distinct ZIKV introductions contributed to the outbreak in Florida and that local transmission likely started in the spring of 2016 -several months before its initial detection. By analyzing surveillance and genetic data, we discovered that ZIKV moved among transmission zones in Miami. Our analyses show that most introductions are phylogenetically linked to the Caribbean, a finding corroborated by the high incidence rates and traffic volumes from the region into the Miami area. By comparing mosquito abundance and travel flows, we describe the areas of southern Florida that are especially vulnerable to ZIKV introductions. Our study provides a deeper understanding of how ZIKV initiates and sustains transmission in new regions.

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confidence: 91%

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confidence: 99%

Multiple introductions of Zika virus into the United States revealed through genomic epidemiology

Grubaugh

Ladner

Kraemer

et al. 2017

Preprint

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“…In the Americas, yellow fever remains a persistent threat (Vasconcelos 2017), dengue has expanded in recent decades (Gubler 2002, Lambrechts et al 2010, Bhatt et al 2013), and chikungunya and Zika have been introduced in the past few years (Cauchemez et al 2014, Zanluca et al 2015, Fauci and Morens 2016). In the contiguous United States, local transmission of dengue, chikungunya, or Zika viruses has occurred recently in Florida and Texas and is a growing public health concern (Ramos et al 2008, Radke et al 2012, Kendrick et al 2014, Dinh et al 2016, McCarthy, 2016, CDC 2017). …”

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confidence: 99%

Modeling the Environmental Suitability for Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus (Diptera: Culicidae) in the Contiguous United States

Johnson

Haque

Monaghan

et al. 2017

Journal of Medical Entomology

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The mosquitoes Aedes (Stegomyia) aegypti (L.)(Diptera:Culicidae) and Ae. (Stegomyia) albopictus (Skuse) (Diptera:Culicidae) transmit dengue, chikungunya, and Zika viruses and represent a growing public health threat in parts of the United States where they are established. To complement existing mosquito presence records based on discontinuous, non-systematic surveillance efforts, we developed county-scale environmental suitability maps for both species using maximum entropy modeling to fit climatic variables to county presence records from 1960–2016 in the contiguous United States. The predictive models for Ae. aegypti and Ae. albopictus had an overall accuracy of 0.84 and 0.85, respectively. Cumulative growing degree days (GDDs) during the winter months, an indicator of overall warmth, was the most important predictive variable for both species and was positively associated with environmental suitability. The number (percentage) of counties classified as environmentally suitable, based on models with 90 or 99% sensitivity, ranged from 1,443 (46%) to 2,209 (71%) for Ae. aegypti and from 1,726 (55%) to 2,329 (75%) for Ae. albopictus. Increasing model sensitivity results in more counties classified as suitable, at least for summer survival, from which there are no mosquito records. We anticipate that Ae. aegypti and Ae. albopictus will be found more commonly in counties classified as suitable based on the lower 90% sensitivity threshold compared with the higher 99% threshold. Counties predicted suitable with 90% sensitivity should therefore be a top priority for expanded mosquito surveillance efforts while still keeping in mind that Ae. aegypti and Ae. albopictus may be introduced, via accidental transport of eggs or immatures, and potentially proliferate during the warmest part of the year anywhere within the geographic areas delineated by the 99% sensitivity model.

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“…Concerns have been raised that several other locations of the continental US are at risk of ZIKV transmission, thus triggering a number of studies aimed at identifying populations at highest risk of local transmission [10][11][12][13][14][15][16][17][18][19][20]. In particular, detailed studies based on environmental suitability, epidemiological factors and travel-related case importations have been used to estimated the risk for specific counties in the US [21,22].…”

Section: Introductionmentioning

confidence: 99%

Quantifying the risk of local Zika virus transmission in the continental US during the 2015-2016 ZIKV epidemic

Sun

Zhang

Piontti

et al. 2018

Preprint

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Background: Local mosquito-borne Zika virus (ZIKV) transmission has been reported in two counties of the continental United State (US), prompting the issuance of travel, prevention, and testing guidance across the continental US. Large uncertainty, however, surrounds the quantification of the actual risk of ZIKV introduction and autochthonous transmission across different areas of the US. Method: We present a framework for the projection of ZIKV autochthonous transmission in the continental US during the 2015-2016 epidemic, using a data-driven stochastic and spatial epidemic model accounting for seasonal, environmental and detailed population data. The model generates an ensemble of travel-related case counts and simulate their potential to trigger local transmission at individual level. Results: We estimate the risk of ZIKV introduction and local transmission at the county level and at the 0.025• ×0.025• cell level across the continental US. We provide a risk measure based on the probability of observing local transmission in a specific location during a ZIKV epidemic modeled after the one observed during the years 2015-2016. The high spatial and temporal resolutions of the model allow us to generate statistical estimates of the number of ZIKV introductions leading to local transmission in each location. We find that the risk is spatially heterogeneously distributed and concentrated in a few specific areas that account for less than 1% of the continental US population. Locations in Texas and Florida that have actually experienced local ZIKV transmission are among the places at highest risk according to our results. We also provide an analysis of the key determinants for local transmission, and identify the key introduction routes and their contributions to ZIKV spread in the continental US. Conclusions: This framework provides quantitative risk estimates, fully captures the stochasticity of ZIKV introduction events, and is not biased by the under-ascertainment of cases due to asymptomatic infections. It provides general information on key risk determinants and data with potential uses in defining public health recommendations and guidance about ZIKV risk in the US.

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Estimating the subcritical transmissibility of the Zika outbreak in the State of Florida, USA, 2016

Cited by 37 publications

References 12 publications

Multiple introductions of Zika virus into the United States revealed through genomic epidemiology

Multiple introductions of Zika virus into the United States revealed through genomic epidemiology

Modeling the Environmental Suitability for Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus (Diptera: Culicidae) in the Contiguous United States

Quantifying the risk of local Zika virus transmission in the continental US during the 2015-2016 ZIKV epidemic

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