Molecular epidemiological characteristics of norovirus in diarrhea cases in Guangzhou

Objective To analyze the molecular epidemiological characteristics of norovirus isolated from diarrhea cases in Guangzhou. Methods Two hospitals in Guangzhou were selected as sentinels during 2014-2015. Each hospital was required to collect 3 stools samples per week from children aged 5 years and 5 years respectively. The samples were sent to Guangzhou Center for Disease Control and Prevention for the detection of norovirus nucleic acid. Then, all the positive samples were sequenced for homology analysis. Epidemiological data of the outbreaks caused by norovirus between 2014 and 2015 were collected from the Information System of Communicable Disease and Public Health Emergency of China, and the epidemiological characteristics were analyzed. Results Among the 732 samples collected, 136 were norovirus positive (18.58%). The positive rate varied with age (2=20.39, P=0.001), and the positive rate in age group 5 years was highest (24.21%). 136 norovirus positive samples were genotyped, in which 133 (97.80%) belonged to genogroup Ⅱ, 3 (2.20%) belonged to genogroup Ⅰ.Four positive samples in 2014 and 5 positive samples in 2015 were further sequenced. The main variant strains were GⅡ.4 Sydney_2012(75.00%) in 2014 and GⅡ.17(55.60%) in 2015. GⅡ genotype was the main pathogen causing 60.80% of 23 outbreaks. Conclusion Norovirus GⅡ was the major pathogen causing infection in Guangzhou, and the predominant strains were GⅡ.4 Sydney_2012 variant in 2014 and GⅡ.17 variant in 2015.