Analysis of the 2025 Thunderstorm Asthma Outbreak in Ningxia, China: Meteorological Trigger Mechanisms and Multicenter Emergency Department Presentation Patterns

Background: Thunderstorm asthma is characterized by sudden surges in asthma exacerbations following convective storm activity during periods of elevated aeroallergen exposure. Proposed mechanisms involve pollen rupture and the generation of respirable allergenic particles driven by strong outflow winds and abrupt increases in humidity. On 11 September 2025, a severe thunderstorm occurred in Yinchuan, Ningxia, China, coinciding with an extreme Artemisia pollen season and followed by a marked increase in asthma-related emergency department (ED) visits across multiple hospitals. Objectives: To characterize the meteorological conditions, background pollen exposure, and multicenter ED presentation patterns associated with a thunderstorm asthma outbreak in northwest China. Methods: Meteorological parameters, including temperature, relative humidity, wind speed, gust velocity, and radar reflectivity, were obtained from the Yinchuan Meteorological Bureau. Artemisia pollen concentrations were derived from regional aerobiological monitoring data. Hourly asthma-related ED visits within 30 hours after the thunderstorm were collected from three major public hospitals and compared with corresponding baseline levels from the same calendar period in 2022–2024. Results: Artemisia pollen concentrations reached annual peak levels (approximately 4,800–5,000 grains/mm²) prior to the storm. At 15:54 local time, the thunderstorm was associated with a rapid temperature decrease of 8.3°C, a sharp rise in relative humidity to 53%, gust wind speeds up to 13.1 m/s, and radar reflectivity exceeding 60 dBZ. Beginning at 18:00, all three hospitals experienced a synchronous increase in asthma-related ED visits, with peaks occurring between 21:00 and 00:00. Approximately 2,160 asthma cases were recorded within 30 hours after the storm, substantially exceeding baseline levels. Females accounted for 52.4% of cases, with women aged 18–40 years comprising the largest subgroup. Among males, the highest proportions were observed in children and adolescents aged 0–9 and 10–17 years. Conclusions: This thunderstorm asthma outbreak in Yinchuan was associated with the convergence of intense convective meteorological dynamics and extreme Artemisia pollen exposure, resulting in a rapid, multicenter surge in asthma-related ED visits. These findings highlight the importance of integrating meteorological and aerobiological data into early warning systems to mitigate the health impacts of thunderstorm asthma in high-risk regions.