Da introdução ao estabelecimento de Aedes aegypti e da dengue em uma área urbana do Sul do Brasil: padrões espaço – temporais e fatores de risco

Abstract

Dengue is an arboviral disease endemic in Brazil that, in recent years, has expanded into temperate climate in the southern region of the country. Porto Alegre, the capital of Rio Grande do Sul, where dengue emergence is relatively recent, provides a opportune location to investigate the dynamics of the Aedes aegypti and dengue transmission within this new climatic context. Accordingly, this study aimed to describe the introduction, expansion, and establishment of the vector and dengue in the municipality between 2001 and 2021, and identify factors associated with their dynamics, through the integration of epidemiological, entomological, environmental, socioeconomic, and demographic data. Documentary analysis were conducted, along with annual space–time scan statistics to detect high-risk clusters and Bayesian statistical models incorporating spatial random effects defined at the neighbourhood level and monthly temporal random effects. In Porto Alegre, Ae. aegypti was first detected in 2001 and, over subsequent years, spread throughout the municipality, achieving wide distribution by 2016. Despite this, local transmission was recorded only from 2010 onwards. Regarding spatio-temporal distribution, dengue and Ae. aegypti exhibited heterogeneity, with clusters occurring more frequently in summer and autumn, although clusters were also observed during winter. At the intra-municipal level, dengue risk was positively associated with vector density and with interactions involving human population density, the proportion of poor households, and imported cases. Urbanisation and mean terrain elevation were positively associated with vector abundance, whereas the Enhanced Vegetation Index (EVI) showed a negative association. In terms of monthly temporal dynamics, dengue risk increased with the minimum temperature of the previous month, the number of imported cases, and the mean number of female Ae. aegypti. Mosquito counts were also positively associated with minimum temperature and accumulated precipitation in the previous month. El Niño showed a positive association with both dengue incidence and vector abundance, contributing to the explanation of interannual variability in transmission. The findings indicate the successful establishment of the vector and dengue in Porto Alegre, marked by seasonality, spatial heterogeneity, and associations with climatic, socioeconomic, and demographic factors, as well as vector density and imported cases. These results highlight the multifactorial and socially mediated nature of dengue transmission and reinforce the need for intersectoral and territorially targeted surveillance and control strategies.