Abstract:

Objective To analyze the epidemiological characteristics and management of varicella outbreaks in Changsha City for references in following planning targeted prevention and control measures for this prevalence. Methods The data of epidemiological investigation reports and management on varicella outbreaks reported by the Centers for Disease Control and Prevention in different districts and counties of Changsha City were collected from 2012 to 2022, and then analyzed regarding the characteristics of temporal, regional and population distribution of chickenpox outbreaks, profile of class aggregation, vaccination coverage, reporting interval, epidemic scale and management procedures. Results From 2012 to 2022, a total of 101 varicella outbreaks were reported in Changsha, with 3 236 cases reported. No death occurred. The outbreak peaked between October and December, with reported incidents accounting for 62.38% (63/101) of the year. The incidents and cases were the highest in Liuyang City, accounting for 56.44% (57/101) and 53.86% (1 743/3 236), respectively. The main place of outbreak was primary school, with 78.22% (79/101) of incidents and 83.16% (2 691/3 236) of cases reported. Among the 100 outbreaks of varicella the occurred in schools, cluster classes accounted for 13.37% (325/2 431), with the highest in kindergarten (21.51%, 37/172). In addition, 57 outbreaks occurred in schools were investigated for vaccination status, the vaccination coverage was 27.63% (454/1 643). The median case number of outbreaks was 27 (19, 38), and median interval between the onset of the first case and reporting of the outbreak was 17 (8, 21) days. The median duration of outbreak was 32 (20, 49) days. The time interval between the onset of the first case and reporting of the epidemic as well as duration of the outbreak presented an increasing trend from 2012 to 2022 (Z=2.516, 2.606, both P<0.05). Conclusion Outbreaks of varicella in Changsha City tended to fall from initial rising, and generally occurred in primary schools. The vaccination coverage remains relatively lower, and the overall reporting interval and duration of the epidemic indicate an increasing trend. These findings suggest that following efforts should focus on improving vaccination coverage, early diagnosis and timely reporting.

Key words: Varicella, Outbreak, Epidemic characteristics, Epidemic response, Changsha City