Factors Associated With the Emergence and Spread of Visceral Leishmaniasis in the State of São Paulo, Brazil.

INTRODUCTION

Visceral leishmaniasis (VL), once considered a rural disease in Brazil, has progressively urbanised, particularly in the state of São Paulo (SSP), where the first urban cases emerged after the detection of the vector Lutzomyia longipalpis in 1997.

METHODS

This study explores the environmental, climatic, socioeconomic, and infrastructural factors associated with the expansion and establishment of VL in urban areas of SSP. For the statistical analysis, two types of models were developed. First, for all municipalities (with or without VL), the logistic regression model was used. Second, for the municipalities in which VL occurred between 1999 and 2012, a multilevel logistic regression model was used, accounting for repeated measurements (VL occurrence or non-occurrence in each municipality) over time. For both models, the associations between exposure variables and the outcome are expressed as odds ratios (OR) and their respective 95% CIs.

RESULTS

We found that the presence of railways, highways, and sugarcane cultivation areas, as well as high annual temperatures and evapotranspiration rates, were associated with VL occurrence. Conversely, lower VL rates were associated with higher rainfall, higher altitude, and more rainy days.

CONCLUSIONS

We conclude that unplanned urbanisation, poverty, population mobility, and climate change have facilitated the spread of the disease in São Paulo. The results highlight the need for integrated surveillance and control strategies that consider the socioenvironmental determinants to prevent further expansion of VL to other vulnerable urban areas of São Paulo State and bordering states.