After the epidemic: Zika virus projections for Latin America and the Caribbean

Abstract

Background: Zika is one of the most challenging emergent vector-borne diseases, yet its future public health impact remains unclear. Zika was of little public health concern until recent reports of its association with congenital syndromes. By 3 August 2017 ∼217,000 Zika cases and ∼3,400 cases of associated congenital syndrome were reported in Latin America and the Caribbean. Some modelling exercises suggest that Zika virus infection could become endemic in agreement with recent declarations from the The World Health Organisation.

Methodology/principal findings: We produced high-resolution spatially-explicit projections of Zika cases, associated congenital syndromes and monetary costs for Latin America and the Caribbean now that the epidemic phase of the disease appears to be over. In contrast to previous studies which have adopted a modelling approach to map Zika potential, we project case numbers using a statistical approach based upon reported dengue case data as a Zika surrogate. Our results indicate that ∼12.3 (0.7-162.3) million Zika cases could be expected across Latin America and the Caribbean every year, leading to ∼64.4 (0.2-5159.3) thousand cases of Guillain-Barré syndrome and ∼4.7 (0.0-116.3) thousand cases of microcephaly. The economic burden of these neurological sequelae are estimated to be USD ∼2.3 (USD 0-159.3) billion per annum.

Conclusions/significance: Zika is likely to have significant public health consequences across Latin America and the Caribbean in years to come. Our projections inform regional and federal health authorities, offering an opportunity to adapt to this public health challenge.

Fig 1. Mean monthly estimates.

Estimated mean monthly Zika virus (ZIKV) cases the total population for an average year at a 0.5 × 0.5 degree resolution. Blank cells indicate risk-free areas. This Figure was created using ArcGIS Desktop 10.3 based on the model outputs projected onto a 0.5 × 0.5 grid. The shapefile for the countries was obtained using the wrld_simpl layer of the maptools R package.

Fig 2. Mean annual cycle.

Estimated mean annual cycle of ZIKV infections in the six countries with the highest predicted health burden.

Fig 3. Epidemic-prone regions.

Location of areas of high variability (i.e. epidemic) in Zika incidence. Blank cells indicate a relative standard deviation lower than one. This Figure was created using ArcGIS Desktop 10.3 based on the model outputs projected onto a 0.5 × 0.5 grid. The shapefile for the countries was obtained using the wrld_simpl layer of the maptools R package.

Fig 4. Effects of El Niño.

(A) Ratio of an average El Niño month to an average non-El-Niño month. (B) Ratio of an average strong El Niño month to an average non-El-Niño month. Blank cells indicate a ratio lower than one. This Figure was created using QGIS Desktop 2.0 based on the model outputs projected onto a 0.5 × 0.5 grid. The shapefile for the countries was obtained using the wrld_simpl layer of the maptools R package.