Projecting the end of the Zika virus epidemic in Latin America: a modelling analysis

Abstract

BackgroundZika virus (ZIKV) emerged in Latin America and the Caribbean (LAC) region in 2013, with serious implications for population health in the region. In 2016, the World Health Organization declared the ZIKV outbreak a Public Health Emergency of International Concern following a cluster of associated neurological disorders and neonatal malformations. In 2017, Zika cases declined, but future incidence in LAC remains uncertain due to gaps in our understanding, considerable variation in surveillance and the lack of a comprehensive collation of data from affected countries.MethodsOur analysis combines information on confirmed and suspected Zika cases across LAC countries and a spatio-temporal dynamic transmission model for ZIKV infection to determine key transmission parameters and projected incidence in 90 major cities within 35 countries. Seasonality was determined by spatio-temporal estimates of Aedes aegypti vectorial capacity. We used country and state-level data from 2015 to mid-2017 to infer key model parameters, country-specific disease reporting rates, and the 2018 projected incidence. A 10-fold cross-validation approach was used to validate parameter estimates to out-of-sample epidemic trajectories.ResultsThere was limited transmission in 2015, but in 2016 and 2017 there was sufficient opportunity for wide-spread ZIKV transmission in most cities, resulting in the depletion of susceptible individuals. We predict that the highest number of cases in 2018 would present within some Brazilian States (Sao Paulo and Rio de Janeiro), Colombia and French Guiana, but the estimated number of cases were no more than a few hundred. Model estimates of the timing of the peak in incidence were correlated (p < 0.05) with the reported peak in incidence. The reporting rate varied across countries, with lower reporting rates for those with only confirmed cases compared to those who reported both confirmed and suspected cases.ConclusionsThe findings suggest that the ZIKV epidemic is by and large over within LAC, with incidence projected to be low in most cities in 2018. Local low levels of transmission are probable, but the estimated rate of infection suggests that most cities have a population with high levels of herd immunity.Electronic supplementary materialThe online version of this article (10.1186/s12916-018-1158-8) contains supplementary material, which is available to authorized users.

Zika virus during pregnancy: From maternal exposure to congenital Zika virus syndrome

“…16 The risk of a new epidemic exists in all areas where Aedes competent mosquitoes are endemic and where the population is nonimmune (although it is currently unclear whether immunity is protective or might induce ADE). 17 ZIKV was first limited to enzootic circulation between nonhuman primates and sylvatic Aedes mosquitoes, before it gained the capacity to be transmitted by human adapted Aedes spp mosquitoes. 18 Since ZIKV has proven to adapt rapidly to new hosts and vectors, however, it is possible that ZIKV may emerge or reemerge in other settings than those mentioned above.…”

Inferring the ecological drivers of arboviral outbreaks

“…Multiple facets of serological, spatial, phylogenetic or surveillance data can be linked to better elucidate the underlying mechanisms of disease, e.g. Kucharski et al (2018); Wesolowski et al (2015). Systems of ordinary differential equations have already been extensively fit to empirical data (Chowell et al, 2007;Lourenço et al, 2017;O'Reilly et al, 2018;Tuncer et al, 2018).…”

“…Kucharski et al (2018); Wesolowski et al (2015). Systems of ordinary differential equations have already been extensively fit to empirical data (Chowell et al, 2007;Lourenço et al, 2017;O'Reilly et al, 2018;Tuncer et al, 2018). However these deterministic frameworks fail to capture the inherent stochasticity and spatio-temporal heterogeneities of arboviral disease, and place strong implicit assumptions on vector ecology.…”

Zika virus seroprevalence declines and neutralization antibodies wane in adults following outbreaks in French Polynesia and Fiji

“…From February 1 to November 18, 2016, due to its rapid spread and association with birth defects, microcephaly in new-borns and Guillain-Barré syndrome in adults 7 the WHO declared ZIKV a Public Health Emergency of International Concern 8 . At the end of 2016, outbreaks had declined in most of the countries recently affected 9 . However, ZIKV was still circulating in 2018 in several countries, including Fiji and Tonga in the Pacific region 10 .…”

“…It has been suggested that infection with ZIKV confers long-term immunity, which lasts several years. If so, the high level of seroprevalence in affected countries may provide herd immunity such that the current ZIKV epidemic is over in many locations and the virus will not be able to re-emerge for decades to come 2,9,13,15 . Recent evidence suggests that neutralizing antibodies can distinguish between ZIKV and dengue virus (DENV) -a closely related Flavivirus -and that the immune response following ZIKV infection can persist over a year 16,17 .…”