A influência de variáveis climáticas e sazonalidade na incidência de zika vírus na região sul do Brasil

Abstract

Introduction: Introduction: Zika virus (ZIKV) is an arbovirus of the Flaviviridae family transmitted primarily by Aedes aegypti, whose life cycle is directly influenced by climatic factors such as temperature and precipitation. In the Southern Region of Brazil, historically considered at lower risk for tropical arboviruses, autochthonous transmission was confirmed in 2016, in a context favored by the 2015–2016 El Niño phenomenon. The present study aimed to analyze the relationship between climatic variables and ZIKV incidence in the Southern Region of Brazil. Methodology: This is an ecological epidemiological study based on secondary data from the Notifiable Diseases Information System (SINAN) and the NASA POWER database, covering municipalities in the states of Paraná, Santa Catarina, and Rio Grande do Sul, from 2016 to 2024. Municipalities with populations below 5,000 inhabitants, with fewer than 20 reported cases during the period, and geographically contiguous municipalities with similar climatic characteristics were excluded, selecting the one with the highest proportional incidence. Mean temperature (°C), accumulated precipitation (mm), De Martonne Index (a climatic indicator that relates precipitation and temperature to assess the degree of humidity in a region), and seasons were analyzed. Statistical modeling used a Generalized Linear Model (GLM) for longitudinal data, with negative binomial distribution and first-order autoregressive correlation structure (AR1), with population offset and fixed effects for all predictors. Four models were developed for two distinct temporal periods and for an epidemiological persistence period (having at least one case in each quarter): global period temporal analysis (2016–2024) with 29 municipalities, 2016 temporal analysis with 9 municipalities, and epidemiological persistence analysis in municipalities from 2016 to 2024 with 9 municipalities. Results: The total sample comprised 3,317 cases for the global analysis, 2,109 cases in the 2016 analysis, and 2,679 cases in the continuous notification analysis. Seasonality was the main predictor of incidence across all analyses. Summer and autumn seasons showed consistent and significant association with higher incidence compared to winter, with increases ranging from 92% in the continuous transmission temporal analysis to 3,990% in the 2016 temporal analysis.Continuous climatic variables (precipitation [mm], temperature [°C], and De Martonne Index) showed statistical significance when analyzed without including seasonality, but lost significance when it was included, suggesting that the climatic effect is mediated by seasonal variation. R² values were low, with the highest values from model 2 (precipitation, temperature, and season) at 0.004 and 0.197. Conclusion: Seasonality constitutes the main climatic predictor of ZIKV incidence in the Southern Region, with case concentration in summer and autumn. The persistence of cases in nine municipalities throughout the entire period indicates continuous viral circulation in a subtropical region. The findings reinforce the need for intensified epidemiological surveillance and vector control during warmer seasons, especially in the context of global climate change and the expansion of suitable areas for Aedes mosquitoes.