Emergence of two novel norovirus genotype II.4 variants associated with viral gastroenteritis in China

Noroviruses (NoVs) are the principal cause of epidemic viral gastroenteritis worldwide, including industrialized and developing countries. Eight hundred and fifty sporadic specimens from hospitalized children with acute gastroenteritis and 131 specimens from seven gastroenteritis outbreaks were collected during 2011-2012 in Jiangsu, China. All specimens were tested for the presence of norovirus (NoV) by real time RT-PCR, and in these, 225/850 of sporadic specimens and 76/131 of outbreak specimens were positive. By sequencing, two novel variants termed JS2011/CHN variant and JS2012/CHN variant were found. By complete genome sequencing and phylogenetic analysis confirmed that both JS2011/CHN variant and JS2012/CHN variant shared more than 98% identity with GII.4 New Orleans/2009/USA strain and GII.4 Sydney/2012/AUS. Both of them had mutations in some key sites in nucleotide sequence and amino acid sequence of ORF1-ORF3. Whether two novel variants will cause epidemic of NoV outbreaks in China deserves further attention. A national surveillance network may be needed to identify trends in molecular evolution of NoVs for prevention of future epidemics.