Comparative Study on Two Epidemic Thunderstorm-Asthma Events: A Retrospective Analysis of Cases in Yulin in 2022 and 2025

INTRODUCTION: Thunderstorm asthma remains an under-investigated public health concern in Northwestern China, a region characterized by high mugwort pollen levels and prevalent allergic rhinitis. No prior studies have systematically compared local outbreaks. This study retrospectively analyzes and compares the clinical characteristics of two major TA events in Yulin, occurring on September 9, 2022, and September 8, 2025. Methods：Patient data were obtained from Yulin Hospital, the First Affiliated Hospital of Xi'an Jiaotong University. Case numbers were retrieved from the Hospital Information System, while detailed clinical records of hospitalized patients were sourced from the medical records database. Results：The 2025 visit data for allergic respiratory diseases demonstrate a distinct seasonal pattern. The highest monthly number of visits throughout the year occurred in September, with a total of 6,831 visits . Daily visit counts within September showed a marked surge. The number of visits on September 8, 9, and 10 were 707, 634, and 419, respectively, totaling 1,760 visits over these three days. Similarly, during the thunderstorm period in September 2022, emergency visits surged to 2,185 cases. Monthly data for 2022 showed a distinct peak in September, with 5,647 visits. Pollen monitoring revealed a bimodal distribution, with concentrations sharply rising to 1,488 grains/1000mm² on September 8. Among 93 hospitalized patients, 41.9% had no prior asthma diagnosis, while 70.9% had allergic rhinitis and 59.1% were sensitized to mugwort pollen. In addition, a comparison of the allergen sensitization profiles in hospitalized thunderstorm asthma patients between 2022 and 2025 revealed that mugwort remained the predominant allergen, with positive rates of 59.1% in 2022 and 60.7% in 2025. Conclusion：The findings confirmed TA as a significant public health threat in Northwest China, driven by the convergence of mugwort pollen exposure and thunderstorm conditions. These results highlighted the urgent need for integrated early-warning systems in susceptible regions.