Influence of climate and heatwaves on dengue transmission in Sao Paulo and Natal, Brazil

PLOS One | https://doi.org/10.1371/journal.pone.0334838 October 24, 2025 3 / 13 vulnerability. This study investigates the short-term associations between heatwaves and dengue incidence in Brazil, focusing on two urban centers with distinct climatic and socioeconomic profiles. We analyze data from São Paulo and Natal, two dengue-endemic cities in Brazil experiencing rising case numbers, to: (1) evaluate the impact of temperature, precipitation, and heatwaves on dengue incidence; (2) compare patterns across contrasting regional contexts; and (3) evaluate whether heatwaves could serve as early indicators of impending outbreaks. By examining heatwaves as discrete climatic stressors, this study contributes new evidence on how climate extremes – beyond long-term averages – may shape arbovirus dynamics in urban environments. Materials and methods Study area and data collection São Paulo/SP and Natal/RN, which are hotspots for dengue transmission in the Latin American region [21]. In 2024 alone (up to September), São Paulo recorded more than two million cases of dengue fever and 1,600 deaths during this period [21]. In Natal, the capital of Rio Grande do Norte State, dengue reappeared in 1996. Since that time, the city has expe- rienced recurring outbreaks, and in 2024, the number of dengue cases surged by 160% compared to the corresponding period in 2023 [21]. We collected meteorological information and dengue cases of both cities (Fig 1). These are two cities

with very different climatic and socioeconomic conditions. The characteristics of each are described in Table 1. At approx- imately 12 million inhabitants, São Paulo is one of the most populous cities in the world [22]. São Paulo is Brazil’s major financial and economic center, contributing about 11.4% of total Brazilian gross domestic product [22]. Within the city of Natal, additional arboviruses, including Zika virus and chikungunya, were simultaneously present, with initial occurrences documented in 2015. Regarding these infections, during the period from 2015 to 2016, Natal-RN accounted for over half of the recorded morbidity burden in Rio Grande do Norte and approximately one-third of verified microcephaly cases linked to Zika virus transmission. We gathered climatic data from weather stations in the municipalities of São Paulo and Natal, Brazil [23], covering the period from 2014 to 2023. Daily meteorological readings from each station were aggregated by week, and the arithmetic mean across all stations was calculated to produce overall weekly values for ambient temperature (mean, minimum, and maximum), rainfall, and the number of rainy days. Concerning heatwaves, we adhere to the definition provided by Seah et al. [24], who describe them in their research as “continuous intervals of elevated temperatures occurring within each Fig 1. Study area in Brazil. Left: Sao Paulo city, capital of Sao Paulo State. Right: Natal city, capital of Rio Grande do Norte State. Source of map base

layers (public domain): IBGE: https://www.ibge.gov.br/geociencias/cartas-e-mapas/mapas-estaduais.html and USGS EROS (Earth Resources Observa- tory and Science Center): https://earthexplorer.usgs.gov/ CC BY 4.0 license. https://doi.org/10.1371/journal.pone.0334838.g001