Associations between COVID-19 Incidence and Environmental Stressors in Brazil: A Nationwide Study from 2020 to 2022

Leona Hoffmann^1*Ludmilla Viana Jacobson²Thilo Erbertseder³Moritz Berger^4,5Jörn Rittweger¹Rochelle Schneider^6,7

• ¹German Aerospace Center (DLR), Cologne, Germany
• ²Universidade Federal Fluminense, Niteri, Brazil
• ³Deutsches Zentrum fur Luft- und Raumfahrt DLR Deutsches Fernerkundungsdatenzentrum, Oberpfaffenhofen, Germany
• ⁴Universitat Bonn Institut fur Medizinische Biometrie Informatik und Epidemiologie, Bonn, Germany
• ⁵Universitat Heidelberg, Heidelberg, Germany
• ⁶european space agency (ESA), Frascati, Italy
• ⁷London School of Hygiene & Tropical Medicine, London, United Kingdom

Background: Environmental stressors such as temperature (Temp), relative humidity (RHumid), and fine particulate matter (PM2.5) may influence the incidence of COVID-19. While many studies have examined these associations in Europe and Asia, research in Brazil—a country with diverse climatic zones and a high burden of COVID-19—remains limited. Objective: This study aimed to assess the associations between environmental stressors and COVID-19 incidence at the municipality level across Brazil over a three-year period, differentiating between climate zones and pre-Omicron/Omicron periods. Methods: We utilized a generalized additive model (GAM) framework to analyze monthly COVID-19 incidence while adjusting for population size, spatial structure, and temporal trends. Distributed lag nonlinear models (DLNM) were used to evaluate lagged exposure-response associations. Separate models were fitted for five climate zones to assess regional variations. Results: In the overall analysis, Temp was positively associated with COVID-19 incidence (relative risk RR 2.47, 95% confidence interval (2.04, 2.91)), while PM2.5 (RR 1.03 (0.95, 1.11)) and RHumid (RR 1.02 (0.91, 1.13)) did not demonstrate clear effects. Climate zone-specific analyses revealed diverse effects: Temp had a positive association with COVID-19 in Temperado (TE) (RR 17.9 (15.26, 22.19)) and Tropical Brazil Central (RR 1.87 (1.57, 2.10)), but a negative association in Tropical Nordeste Oriental (RR 0.008 (0.004, 0.012)) and Tropical Zona Equatorial (TZE) (RR 0.12 (0.08, 0.15)) climate zones. RHumid showed varying positive and negative associations depending on the climate zone, while high levels of PM2.5 are positive associated with COVID-19 incidence in zones TE (RR 2.10 (1.93, 2.28)) and TZE (RR 1.87 (1.54, 2.31)). DLNM results revealed parabolic lag response curves, with extreme values of Temp and RHumid raising risks in certain zones. Significance: Our study provides a comprehensive, long-term analysis of environmental stressors and COVID-19 incidence across diverse climate zones in Brazil. The results reveal considerably spatial and temporal variations in how Temp, RHumid, and PM2.5 influence COVID-19 incidence. These findings emphasize the importance of considering regional climatic conditions when assessing environmental risk factors for COVID-19. Understanding these associations can inform targeted public health interventions and preparedness strategies for future respiratory disease outbreaks.