Epidemiologic characteristics of norovirus outbreaks in Harbin, 2016-2017

Abstract

Objective To understand the epidemiologic characteristics of norovirus outbreaks in Harbin during 2016-2017. Methods Epidemiologic cases reports, investigation reports and laboratory tests of the norovirus outbreaks between Jan., 2016 and Dec., 2017 were collected and the spatial, temporal and population distributions, clinical features and routes of transmission were analyzed. Results A total of 13 norovirus outbreaks were reported during this period. The overall attack rate was 3.6% (421/11 654). All the outbreaks occurred in schools and all cases were students. The minimum age was 3 years old, the maximum was 23 years old, and the average age was (13.7±3.1) years old. Preschoolers had the highest rate, namely 18.3% (102/557), followed by primary school students (8.8%, 208/2 376) and college students (1.3%, 111/8 721). The difference was statistically significant (x2=663.17, P<0.01). There was a small peak from May to June, including of eight outbreaks and 57.2% (241/421) of cases. The main transrmission route was human-to-human. Conclusions Norovincs outbreaks occured in schools and kindergartens. The surveillance for norovirus infection during peak time should be strengthened in schools and kindergartens for effective controlling of epidemics and disease spreading. Key words: Norovirus; Epidemiologic character; Outbreak; Epidemic