Epidemiological characteristics of norovirus outbreaks in Shenzhen during 2005 to 2017

Abstract

Objective To investigate the epidemiological characteristics of norovirus outbreaks in Shenzhen during 2005 to 2017 in order to provide reference for disease control and prevention. Methods Monitoring data of norovirus outbreaks in Shenzhen from January 1, 2005 to December 31, 2017 were collected from Shenzhen Communicable Disease Information System and China Information System for Disease Control and Prevention. Descriptive epidemiological methods were used for data analysis. Results From January 2005 to December 2017, 346 norovirus outbreaks (five or more cases in one community within one week) were reported in Shenzhen, of which 6.36% (22/346) were public health emergency events. Fewer outbreaks were reported during 2006 to 2013 and they were mainly caused by GⅡ.4 genotype, but the number increased sharply since 2014 with 57.80% (200/346) occurred in 2016—2017 and the epidemic genotype changed from GⅡ.4 to GⅡ.17 and GⅡ.2. The outbreaks peaked during November to March (76.88%, 266/346). There were 63.87% (221/346) reported in urban areas, 67.05% (232/346) in nurseries and 23.70% (82/346) in primary/middle schools. Among the 22 public health emergency events, 40.91% (10/22) were caused by person-to-person contacts, 40.91% (10/22) by foodborne transmission and 13.64% (3/22) by waterborne transmission. Moreover, 75.80% (238/314) of the outbreaks in nurseries and primary/middle schools were confined to one classroom and most were due to contact transmission. Conclusions Norovirus outbreaks increased obviously since 2014, which might be related to the changes of the predominant genotype from GⅡ.4 to GⅡ.17 and GⅡ.2. It is necessary to strengthen a comprehensive prevention and control in key units such as nurseries and primary/middle schools in winter and spring. Key words: Norovirus; Outbreak; Public health emergency; Genotype