Epidemiological characteristics of varicella in Xuzhou from 2015 to 2024: surveillance study.

BACKGROUND

Varicella remains a major public health challenge in China, with limited evidence on long-term urban-rural epidemiological trends. This study analyzes varicella characteristics in Xuzhou, Jiangsu, 2015-2024, focusing on incidence, seasonality, and public health emergency events (PHEEs).

METHODS

This surveillance study analyzed population-based varicella case data and public health emergency events (PHEEs) in Xuzhou City, China, from January 2015 to December 2024. Data were extracted from the China Disease Prevention and Control Information System and the National Notifiable Disease Reporting System. Varicella PHEEs were defined as ≥ 10 cases occurring in a collective unit within one week. We employed descriptive statistics, chi-square tests, and chi-square trend tests (for temporal trends of incidence rates) to analyze temporal trends and demographic distribution; the Mann-Kendall trend test was used to assess trends in PHEE-related indicators (duration, reporting latency, and case counts per event).

RESULTS

Annual incidence increased sharply to a peak of 65.01 per 100,000 in 2019, decreased in 2020, transiently rebounded in 2021, and then showed an overall declining pattern through 2024; overall, annual incidence varied significantly over the 10-year period (trend χ2 = 6789.65, p < 0.001). Two peaks emerged: a winter peak (Oct-Jan, 52.74% of cases) and a minor early summer peak (May-Jul, 26.36%). Urban areas had higher case counts but lower attack rates than rural areas (1.52% vs. 1.81%, p < 0.001). Males had an incidence rate 1.24 times that of females (p < 0.001). Children aged 0-14 years accounted for 83.22% of cases, with the highest rate in 5-9-year-olds (219.26/100,000), while adults aged ≥ 30 years showed a significant upward trend in case proportion (trend χ2 = 260.09, p < 0.01). All reported varicella PHEEs emerged in educational sites, 90.29% in primary schools and kindergartens, with 67.96% involving 10-30 cases. Kindergartens had the highest attack rate (5.60%). PHEE duration, case count, and reporting latency correlated strongly (Spearman's ρ=0.97-0.99, p < 0.01).

CONCLUSIONS

Xuzhou's varicella epidemiology features seasonal clustering, age-specific vulnerability, and school-associated outbreaks. Strengthening rural/childhood vaccination and improving school PHEE responses are critical for control.

CLINICAL TRIAL NUMBER: Not applicable.