Risks of high temperature exposure on infectious diseases in Portuguese hospitals

Abstract Background The convergence of climate change and infectious diseases presents a growing public health challenge. As global temperatures continue to climb, the geographical spread of climate-sensitive diseases is shifting, underscoring the necessity for comprehensive early warning systems grounded in a One Health framework. Methods This retrospective observational study analyzed daily maximum temperature from May to September, between 2000 and 2018, in mainland Portugal, at a county level, obtained from a European-level gridded observations dataset. Hospital admissions with a primary diagnosis of infectious and parasitic diseases were sourced from the Hospital Morbidity Database. A distributed lag non-linear model was developed to estimate the immediate and lagged relative risks (RR) of temperature exposure on admissions, focused on a lag of 10 days. Results Our research reveals a 16% (95% CI: 9% - 23%) rise in the RR of hospital admissions due to infectious and parasitic diseases after exposure to extremely high temperatures (39 °C). This elevated risk persists for up to 2 days following exposure, with the second day exhibiting the largest increase at 53% (31% - 80%). Furthermore, our findings indicate a subsequent resurgence in RR, reaching 6% (2% - 11%) 9 days after exposure. Conclusions Our results highlight a short-term effect of extreme temperature exposure on infectious and parasitic disease admissions. This data provides valuable insights to guide policymakers in identifying critical periods of vulnerability and implementing this knowledge into heat early warning systems, contributing to developing effective public health strategies against climate change. Acknowledgments The authors thank Fundação para a Ciência e a Tecnologia (FCT, Portugal) for research grant UIDP/04923/2020 and NOVA National School of Public Health for access to the Hospital Morbidity Database made available for research purposes by Administração Central do Sistema de Saúde, IP (ACSS). Key messages • Exposure to extremely high temperatures increases the risk of admission due to infectious and parasitic diseases by 16%, with a peak occurring two days after exposure. • This data is essential for policymakers to identify and integrate vulnerable periods into early heat warning systems, enhancing effective public health strategies against climate change.