Investigating the associations among environmental stressors and their links to COVID-19 incidence

<strong>Background:</strong> The COVID-19 pandemic has highlighted the importance of environmental stressors in influencing viral transmission. While existing research has primarily focused on the short-term effects of meteorology and air pollution, there is less evidence on how these factors relate to the occurrence of COVID-19 in different climates. This dissertation addresses this gap by examining the associations between environmental stressors and COVID-19 incidence in Germany and Brazil over a three-year period, covering both rural and urban areas. <br> <strong>Methods:</strong> This work is based on three peer-reviewed papers. The first research paper of this work analyzed the interdependencies among environmental stressors in Baden-Württemberg, Germany, using daily data from 2010 to 2018. The second research paper examined the associations between specific stressors and COVID-19 incidence in the same region during the pandemic (2020-2022) using generalized additive models (GAM). In the third research paper, the analysis was expanded to Brazil, incorporating relative humidity and applying both GAM and distributed lag nonlinear models (DLNM) to monthly data from 2020 to 2022. <br> <strong>Results:</strong> Temperature and PM2.5 were identified as the most consistently influential environmental stressors across different regions, although their impacts varied by pandemic phase and climatic conditions. In temperate Germany, lower temperatures were associated with higher COVID-19 incidence, while in certain climate zones of Brazil higher temperatures and PM2.5 linked with increased COVID-19 case numbers. <br> <strong>Discussion:</strong> The findings highlight the complex and context-dependent associations between environmental stressors and COVID-19 incidence. This research enhances our understanding of the environmental determinants of COVID-19 and highlights the need for studies that are more diverse in terms of geography and climate. Further interdisciplinary research is needed to better understand the causal links between environmental stressors and disease incidence, which is crucial for managing future outbreaks and addressing public health risks in a changing climate.