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 (chi(2), P < 0.05), abdominal pain (chi(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.