Epidemiologic characteristics of noroviruses isolated in outpatients with acute gastroenteritis in Hangzhou area, from 2014 to 2015

Abstract

To explore the epidemiologic characteristics of noroviruses isolated in patients with acute gastroenteritis in Hangzhou between March 2014 and April 2015. Stool specimens and clinical data were collected from 1 109 patients with acute gastroenteritis. Specimens were detected for noroviruses with GⅠand GⅡsubtypes by one-step double real-time RT-PCR. Some of the positive specimens were then randomly selected and amplified by multiplex RT-PCR. Those positive PCR products were sequenced and analyzed phylogenetically for testing the partial capsids of noroviruses. Of the 1 109 stool specimens, positive rate of noroviruses was 26.87% (298/1 109). GⅡgenotype was the major viruses with the proportion as 25.52% (283/1 109), while 1.35% (15/1 109) belonged to GⅠgenotypes. There was no significant difference in the noroviruses detection rate of the different genders (P>0.05). However, in different age groups, GⅡgenotypes were predominant types of noroviruses, and the positive rates of GⅡgenotypes were 16.94% (<5 years-old), 19.45% (5-18 years-old) and 32.26% (≥18 years-old), respectively. In different seasons, noroviruses could be detected all year round, with positive rate as 29.67%-37.08% in the highly epidemic seasons (between December and March of the following year). The distribution trends were seen certain difference between noroviruses-GⅡand GⅠtypes. Additionally, results from the sequence analysis demonstrated that GⅡ-4 genotype was the prevalent strain of GⅡ genotypes, clustered into GⅡ-4/Sydney (46.43%, 13/28) and GⅡ-4/2006b (25.0%, 7/28), while GⅠstrains clustered into GⅠ-1. Noroviruses appeared one of the major pathogens, leading to acute gastroenteritis. G Ⅱgenotypes of noroviruses, especially the G Ⅱ-4/Sydney variant strains and GⅡ-4/2006b variant strains, were considered to be the prevalent strains prevailed in Hangzhou areas from 2014 to 2015.