Seroprevalence for dengue virus in a hyperendemic area and associated socioeconomic and demographic factors using a cross-sectional design and a geostatistical approach, state of São Paulo, Brazil

Abstract

Background: São José do Rio Preto is one of the cities of the state of São Paulo, Brazil, that is hyperendemic for dengue, with the presence of the four dengue serotypes.

Objectives: to calculate dengue seroprevalence in a neighbourhood of São José do Rio Preto and identify if socioeconomic and demographic covariates are associated with dengue seropositivity.

Methods: A cohort study to evaluate dengue seroprevalence and incidence and associated factors on people aged 10 years or older, was assembled in Vila Toninho neighbourhood, São José do Rio Preto. The participant enrolment occurred from October 2015 to March 2016 (the first wave of the cohort study), when blood samples were collected for serological test (ELISA IgG anti-DENV) and questionnaires were administrated on socio-demographic variables. We evaluated the data collected in this first wave using a cross-sectional design. We considered seropositive the participants that were positive in the serological test (seronegative otherwise). We modelled the seroprevalence with a logistic regression in a geostatistical approach. The Bayesian inference was made using integrated nested Laplace approximations (INLA) coupled with the Stochastic Partial Differential Equation method (SPDE).

Results: We found 986 seropositive individuals for DENV in 1322 individuals surveyed in the study area in the first wave of the cohort study, corresponding to a seroprevalence of 74.6% (95%CI: 72.2-76.9). Between the population that said never had dengue fever, 68.4% (566/828) were dengue seropositive. Older people, non-white and living in a house (instead of in an apartment), were positively associated with dengue seropositivity. We adjusted for the other socioeconomic and demographic covariates, and accounted for residual spatial dependence between observations, which was found to present up to 800 m.

Conclusions: Only one in four people aged 10 years or older did not have contact with any of the serotypes of dengue virus in Vila Toninho neighbourhood in São José do Rio Preto. Age, race and type of house were associated with the occurrence of the disease. The use of INLA in a geostatistical approach in a Bayesian context allowed us to take into account the spatial dependence between the observations and identify the associated covariates to dengue seroprevalence.

Keywords: Brazil; Cross-sectional study; Dengue; Geostatiscal analysis; Seroprevalence.

Fig. 1

a: Municipality of São José do Rio Preto, state of São Paulo, Brazil, South America; b: Vila Toninho neighborhood (study area) in the municipality of São José do Rio Preto

Fig. 2

Vila Toninho neighborhood and the distribution of seropositive, seronegative and inconclusive dengue cases, São José do Rio Preto, State of São Paulo, Brazil, 2015–2016

Fig. 3

Posterior mean of the spatial random field of the final model (intercept, covariates and the spatial component for the imputed datasets), considering the first imputed database, Vila Toninho neighbourhood, São José do Rio Preto, state of São Paulo, Brazil, 2015–2016

Fig. 4

Values of the spatial random field related to the positive and negative dengue cases of the final model (intercept, covariates and the spatial component for the imputed datasets), considering the first imputed database; red colour represents negative values and blue, positive values; Vila Toninho neighbourhood, São José do Rio Preto, state of São Paulo, Brazil, 2015–2016