Abstract: Objective To understand the epidemiological characteristics of severe fever with thrombocytopenia syndrome (SFTS) and tick vectors in Zhejiang province of China in 2021. Methods The data on SFTS cases in Zhejiang province in 2021 were obtained from China Information System for Disease Control and Prevention, and descriptive epidemiological methods were used to describe the temporal, population, and regional distributions of SFTS cases. Tick surveillance sites were set up in 8 counties (cities/districts) of Zhejiang province from March to October 2021, and the drag-flag method was used to collect free-living ticks and the body surface examination method for on-host ticks. Excel 2013 and SPSS17.0 softwares were used to perform a statistical analysis of the data on SFTS cases and vector surveillance data, and ArcGIS 10.0 software was used to draw the map of SFTS incidence rate in districts and counties. Results A total of 85 SFTS cases were reported in Zhejiang province in 2021, with a reported incidence rate of 0.15/100 000 and a fatality rate of 8.24% (7/85). The cases were distributed in 23 counties (cities/districts) in 8 prefectures, and the top 3 prefectures in terms of the number of cases were Jinhua (27 cases), Taizhou (27 cases), and Ningbo (11 cases) cities. The cases mainly occurred in April to October, with a peak in May to July. There was no significant difference in incidence rate between the male patients and the female patients (χ²=1.347, P=0.246); as for the age of onset of SFTS, most cases were middle-aged and elderly patients, with a median age of 67 years; most of the patients were farmers, accounting for 80.00% (68/85). The patients with a clear history of tick bites within 2 weeks before SFTS onset accounted for 17.65% (15/85). A total of 590 free-living ticks were collected in the unpopulated rural area, and the mean density of free-living ticks was 18.44 ticks/flag·h. A total of 688 animals were monitored and 2 406 on-host ticks were collected, with a mean density of 3.50 ticks per host. Conclusion Sporadic cases of SFTS are mainly observed in Zhejiang province, with obvious regional and seasonal characteristics. The middle-aged and elderly people and farmers were the main affected populations. Free-living ticks and on-host ticks show a relatively high density as the vector for SFTS.

Key words: Severe fever with thrombocytopenia syndrome, Surveillance, Epidemiological characteristics, Tick vector

摘要： 目的 了解浙江省2021年发热伴血小板减少综合征（SFTS）流行病学特征及蜱媒监测情况。方法 浙江省2021年SFTS病例数据来源于中国疾病预防控制信息系统，采用描述性流行病学方法分析SFTS病例的时间、人群、地区分布特征。2021年3－10月选择浙江省8个县（市、区）设置蜱媒监测点，利用人工布旗法和动物体表检蜱法采集游离蜱和寄生蜱。利用Excel 2013、SPSS 17.0软件对全省SFTS病例和媒介监测数据进行整理、统计分析，运用ArcGIS 10.0软件绘制以区（县）为单位发病率地图。结果 2021年浙江省累计报告SFTS病例85例，报告发病率为0.15/10万，病死率为8.24%（7/85）。病例分布于8个地市的23个县（市、区），报告病例数居前3位的地区为金华市（27例）、台州市（27例）和宁波市（11例）。发病时间主要集中在4－10月，5－7月为发病高峰期。报告病例中男性和女性发病率差异无统计学意义（χ²=1.347，P=0.246）；发病年龄以中老年为主，中位年龄67岁；职业以农民为主，占80.00%（68/85）。发病前2周有明确蜱叮咬史的病例占17.65%（15/85）。农村外环境游离蜱共采集590只，平均游离蜱密度为18.44只/（布旗·人工时）；共计监测动物数量688只（头），采集蜱2 406只，平均寄生蜱密度3.50只/宿主。结论 浙江省SFTS以散发为主，发病具有明显的地区性和季节性，主要发病人群为中老年和农民。传播媒介游离蜱和寄生蜱密度较高。

关键词: 发热伴血小板减少综合征, 监测, 流行特征, 蜱媒