A recent study, published in The Lancet Regional Health – Europe, sheds light on the short-term effects of temperature and precipitation on the incidence of West Nile Neuroinvasive Disease (WNND) in Europe. Conducted by researchers from the E4Warning partners from the Barcelona Supercomputing Center (BSC) and international collaborators, the study utilized a nine-year dataset (2014–2022) to analyze 3,437 WNND cases across 20 European countries.

To estimate the association between lagged meteorological variables and WNND cases, the study employed a space-time-stratified case-crossover design. This design treats each case as its control, comparing exposures during the “hazard period” (the weeks before symptom onset) to exposures in comparable “reference periods.” Cases and controls were matched within the same region, calendar month, and year, as well as by the day of the week, enabling precise control of confounding factors such as geography, long-term trends, and seasonality.

For each case, weekly mean temperature and cumulative precipitation were attributed to the 8 weeks preceding the symptom onset day and matched control days. For instance, if a case occurred on May 17, 2019, in a given region, control days were selected from other Fridays in the same month and year. This method allowed researchers to infer associations between meteorological conditions and WNND incidence.

Meteorological data were obtained from the ERA5-Land climate reanalysis database, produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). Researchers retrieved gridded daily mean temperature and daily cumulative precipitation data for the European continent over the entire study period (2014–2022). ERA5-Land provides atmospheric and land-surface variables with a spatial resolution of approximately 9 km × 9 km. To align with epidemiological data, daily meteorological data were spatially averaged at the NUTS3 level.

Key Findings:

• Temperature and Precipitation as Drivers: Weekly mean temperatures exceeding 25°C (the 90th percentile) were associated with 36.4% of WNND cases, with the strongest effect observed two weeks before symptom onset. Similarly, weekly cumulative precipitation above 40 mm contributed to 13.1% of cases, with a delayed peak effect three weeks before symptom onset.
• Regional Variation: The study highlighted consistent effects of temperature across regions but noted moderate variability in precipitation’s impact, reflecting differences in local ecosystems and mosquito ecology.
• Implications for Early Warning Systems: The findings underline the potential of integrating meteorological data into early warning systems. These systems could enhance preparedness for WNV outbreaks, particularly in areas lacking robust vector and host surveillance infrastructure.

Broader Implications:

This study reinforces the link between climate variability and the transmission of mosquito-borne diseases, emphasizing the need for a One Health approach to address the complex interactions between climate, ecosystems, and human health. The results provide actionable insights for tailoring early warning systems and vector control strategies to mitigate the growing burden of WNV outbreaks in Europe.

For more details, check out the paper: Moirano, G., Fletcher, C., Semenza, J. C., & Lowe, R. (2025). Short-term effect of temperature and precipitation on the incidence of West Nile Neuroinvasive Disease in Europe: a multi-country case-crossover analysis. The Lancet Regional Health – Europe, 48, 101149. https://doi.org/10.1016/j.lanepe.2024.101149

And in the E4Warning Zenodo repository: https://zenodo.org/records/14383572

Our partner and WP leader, Rachel Lowe, ICREA Research Professor and Global Health Resilience (GHR) Group Leader at the Barcelona Supercomputing Center (BSC), was recently interviewed by HERA (Health Emergency Preparedness and Response Authority) and featured on their website: https://ec.europa.eu/newsroom/hera/items/852413/en

HERA is an EU body established to strengthen Europe’s ability to anticipate and respond to health emergencies, particularly in the wake of the COVID-19 pandemic. It aims to ensure the provision of critical medical countermeasures and enhance Europe’s readiness for future health threats.

In the interview, Rachel Lowe discusses the intricate connections between climate change and the outbreaks of climate-sensitive infectious diseases, exploring why these outbreaks are increasing and spreading to new regions, particularly in Europe. She also explains how shifting climate patterns could influence emergency preparedness and response strategies, highlighting the need for proactive, integrated approaches. She shared insights into specific climate-sensitive diseases that pose a potential threat to the EU, including dengue, chikungunya, and West Nile virus, and discussed ongoing efforts like the development of the EpiOutlook platform within the IDAlert project, which is part of the European Climate-Health Cluster. This platform aims to provide early warnings of climatic suitability for various infectious diseases in Europe. They also track the impact of climate change on these diseases in the Lancet Countdown in Europe collaboration.

As part of E4Warning, Professor Lowe also elaborated on her work in developing decision support tools like the D-MOSS (Dengue forecasting Model Satellite-based System) for dengue in endemic regions in collaboration with HR-Wallingford, as well the efforts on integrating different data sources such as citizen science initiatives like Mosquito Alert, which could enhance the monitoring and management of disease vectors across Europe, providing critical support for future public health interventions.

For more details, read the full interview on the HERA website and gain valuable insights into how E4Warning and its partners are addressing the growing challenges posed by climate-sensitive diseases in Europe.