Joint Estimation of Relative Risk for Dengue and Zika Infections, Colombia, 2015-2016

Abstract

We jointly estimated relative risk for dengue and Zika virus disease (Zika) in Colombia, establishing the spatial association between them at the department and city levels for October 2015-December 2016. Cases of dengue and Zika were allocated to the 87 municipalities of 1 department and the 293 census sections of 1 city in Colombia. We fitted 8 hierarchical Bayesian Poisson joint models of relative risk for dengue and Zika, including area- and disease-specific random effects accounting for several spatial patterns of disease risk (clustered or uncorrelated heterogeneity) within and between both diseases. Most of the dengue and Zika high-risk municipalities varied in their risk distribution; those for Zika were in the northern part of the department and dengue in the southern to northeastern parts. At city level, spatially clustered patterns of dengue high-risk census sections indicated Zika high-risk areas. This information can be used to inform public health decision making.

Keywords: Bayesian models; Colombia; Risk maps; Zika virus; conditional auto-regressive prior; dengue virus; multivariate risk models; viruses.

Figure 1

Location of the areas included in joint estimation of relative risk for dengue and Zika virus infections, Colombia, 2015–2016. A) Country of Colombia; inset shows location of Colombia in South America. B) Department of Santander; inset shows location of Santander in Colombia. C) City of Bucaramanga; inset shows location of Bucaramanga in Santander.

Figure 2

Schematic representation of the spatial patterns of dengue and Zika risk revealed by the joint models of relative risk models, Colombia, 2015–2016. A) Model 1; B) model 2; C) model 3; D) model 4; E) model 5; F) model 6; G) model 7; H) model 8. For a set of small areas, high-risk areas are represented in red and low-risk areas are represented in green, depicting several patterns that could or could not be shared for both diseases in the same geographic area.

Figure 3

Incidence rate of dengue and Zika per 100,000 population by age group and sex, Colombia, 2015–2016. A) Department of Santander; B) city of Bucaramanga.

Figure 4

IRs and SIRs for dengue and Zika virus disease, Colombia, 2015–2016. A) Santander IR; B) Santander SIR; C) Bucaramanga IR; D) Bucaramanga SIR. IR, incidence rate; SIR, standardized incidence rate.

Figure 5

Posterior mean RR and 95% credible interval (CrI) of RR >1 (95% CrI RR >1), from model 5 for the department of Santander and from model 7 for the city of Bucaramanga, Colombia, 2015–2016. A) Posterior mean RR for Santander; B) 95% CrI RR >1 for Santander; C) posterior mean RR for Bucaramanga; D) 95% CrI RR >1 for Bucaramanga. RR, relative risk.