[Analysis on the epidemiological characteristics and prognosis of sequelae of Japanese encephalitis in Zhejiang Province from 2017 to 2024].

Objective

To clarify the epidemiological characteristics and clinical manifestations of Japanese encephalitis (JE) in Zhejiang Province from 2017 to 2024, and assess the prognosis of patients with sequelae of JE.

Methods

A descriptive analysis was conducted using data from the China Disease Control and Prevention Information System to assess the epidemiological characteristics and clinical manifestations of JE cases in Zhejiang Province from 2017 to 2024. Follow-up evaluations were conducted via face-to-face interviews or telephone calls to assess patients' prognosis with the Liverpool Outcome Score (LOS). Potential factors associated with different prognostic outcomes were further analyzed.

Results

A total of 53 JE cases were reported from 2017 to 2024 in Zhejiang Province, with an average annual reported incidence rate of 0.11 cases per million population, showing a significant decrease over the years (χ2trend=22.81, P<0.001). The majority of cases occurred between June and August, accounting for 92.45% (49/53). Geographically, the annual incidence per million was highest in Wenzhou (0.20), Ningbo (0.19), and Jinhua (0.19). The population distribution was predominantly composed of non-local residents (30 cases, 56.60%), and the majority of occupations were workers (13 cases, 24.53%). The median age M (Q1, Q3) was 22.0 (8.0, 31.0) years. There were 29 cases aged ≥18 years (54.72%), and their proportion showed a fluctuating upward trend from 1/6 in 2019 to 2/2 in 2024. The clinical classification of cases revealed 15 mild cases (28.30%), 13 moderate cases (24.53%), 19 severe cases (35.85%), and 6 critical cases (11.32%). The main clinical manifestations included fever (52 cases, 98.11%), lethargy (50 cases, 94.34%), somnolence (40 cases, 75.47%), consciousness disturbance (39 cases, 73.58%), and headache (30 cases, 56.60%). During follow-up, there were 10 JE-related deaths [with a mortality rate of 18.87%, median survival time of 3.5 (2.0, 7.0) months, accounting for 9/10 of adults], and 4 cases with residual sequelae (with a sequelae rate of 9.30%, median duration of 82.5 months, accounting for 1/4 of adults), primarily manifested as poor language communication and behavioral disturbances. The ≥18-year age group (χ2=5.85, P=0.016) and unvaccinated group (χ2=4.58, P=0.032) showed poorer clinical outcomes.

Conclusion

From 2017 to 2024, the incidence of JE in Zhejiang Province remains at a low level, with the increasing trend of the proportion of adult cases. Given the poor prognosis among adults with JE, it is essential to strengthen the prevention and control of JE in adults while maintaining the high vaccination coverage for children.