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

Linh Dinh,Hiroshi Nishiura,Gerardo Chowell,Kenji Mizumoto

doi:10.1186/s12976-016-0046-1

Abstract

BackgroundFlorida State has reported autochthonous transmission of Zika virus since late July 2016. Here we assessed the transmissibility associated with the outbreak and generated a short-term forecast.MethodsTime-dependent dynamics of imported cases reported in the state of Florida was approximated by a logistic growth equation. We estimated the reproduction number using the renewal equation in order to predict the incidence of local cases arising from both local and imported primary cases. Using a bootstrap method together with the logistic and renewal equations, a short-term forecast of local and imported cases was carried out.ResultsThe reproduction number was estimated at 0.16 (95 % Confidence Interval: 0.13, 0.19). Employing the logistic equation to capture a drastic decline in the number of imported cases expected through the course of 2016, together with the low estimate of the local reproduction number in Florida, the expected number of local reported cases was demonstrated to show an evident declining trend for the remainder of 2016.ConclusionsThe risk of local transmission in the state of Florida is predicted to dramatically decline by the end of 2016.

Highlights

Florida State has reported autochthonous transmission of Zika virus since late July 2016
We carried out a risk assessment of Zika transmission in Florida aimed to estimate the extent of local transmission potential of Zika, e.g., are on-going local chains of transmission sustained in Florida? We generated a shortterm forecast of the expected burden of Zika for the remainder of 2016
The reproduction number R of local Zika virus transmission in Florida was estimated to lie in the range of 0.13–0.19, likely reflecting primarily limited transmission potential and perhaps the effects of intensive vector control efforts including the strong advice of draining standing water, covering clothing and bare skin with repellent, and covering windows with screens

Summary

Introduction

Florida State has reported autochthonous transmission of Zika virus since late July 2016. We assessed the transmissibility associated with the outbreak and generated a short-term forecast. The state of Florida has reported over 735 travel-related Zika cases since February 2016, becoming the first state in the continental USA to report multiple laboratoryconfirmed autochthonous cases of Zika [1]. To assess the risk of infection for local residents and travelers, it is critical to understand whether local transmission is sustained as well as forecast the duration and size of the outbreak. We carried out a risk assessment of Zika transmission in Florida aimed to estimate the extent of local transmission potential of Zika, e.g., are on-going local chains of transmission sustained in Florida? We carried out a risk assessment of Zika transmission in Florida aimed to estimate the extent of local transmission potential of Zika, e.g., are on-going local chains of transmission sustained in Florida? We generated a shortterm forecast of the expected burden of Zika for the remainder of 2016.

Methods

Results

Discussion

Conclusion