Clinical and Epidemiologic Characteristics of Norovirus GII.4 Sydney during Winter 2012–13 in Beijing, China following Its Global Emergence

BACKGROUND: Limited information is available on the molecular epidemiology of GII.4 Sydney-associated diarrhea in China in the winter of 2012–13 during the global epidemic associated with the emergence of GII.4 Sydney. METHODS: Fecal specimens collected from 171 diarrhea outpatients (one from each) between late October 2012 and the middle of March 2013 were examined for NoV by reverse transcription-polymerase chain reaction and sequences corresponding to both the NoV partial polymerase and partial capsid regions were analyzed phylogenetically. Clinical characteristics of GII.4 Sydney cases versus other NoV-positive cases detected in a previous study were compared statistically. RESULTS: Twenty-six (15.2%, 26/171) outpatients with diarrhea were infected with NoV. Twenty-two of the 26 (84.6%) identified NoV strains clustered into GII.4 Sydney. There was a significant difference in symptoms of fever (χ(2), P<0.05 ), abdominal pain (χ(2), P<0.05 ) and diarrhea frequency (Mann-Whitney U test, P<0.05) between the GII.4 Sydney case group and other NoV-positive case group. CONCLUSIONS: The new NoV variant, GII.4 Sydney, has been circulating in Beijing, China and became the predominant strain in the winter of 2012–13. GII.4 Sydney causes severe fever, abdominal pain and higher diarrhea frequency clinically compared to other NoV infections.