[Molecular characteristics of acute gastroenteritis outbreaks caused by norovirus, in Jiangsu province].

Objective: To study both the epidemiologic and molecular characteristics of outbreaks caused by norovirus (NoV) with its variants, in Jiangsu.

Methods: 67 specimens from seven gastroenteritis outbreaks were collected from October 2012 to March 2013 in Jiangsu. NoV gene group was detected by Real-Time RT-PCR. NoV portions of RdRp gene and VP1 gene were amplified under RT-PCR.

Results: Seven gastroenteritis outbreaks were caused by NoV. Among all the fecal specimens,45 (67.2%) showed positive to NoV G II. Study on the genotype was conducted through analyzing the nucleotide sequence of RdRp gene. Based on the RdRp region, 7 strains appeared to be G II, with 3 and 38 strains belonged to G II.4--Sydney variants. Results from phylogenetic analysis confirmed that 38 variants shared 99% identity with G II.4--Sydney. We also amplified the VP1 genes from 6 variants and comparing with 9 epidemic strains on the sequence amino acid sequence. All the strains showed mutation in amino acid sequence at some key sites which were closely related to the forming of neutralizing epitopes.

Conclusion: The short interval periods between all 7 NoV outbreaks with identical viral strain indicated the emergence of a new NoV variant in Jiangsu province,that had caused a number of epidemics abroad. Results from our study suggested that the development of monitoring programs on this novel G II.4--Sydney variant should be a part of the NoV surveillance in Jiangsu province or even in the country.