Clinical and molecular epidemiology of norovirus infection in childhood diarrhea in China.

A prospective investigation was carried out among pediatric outpatients and inpatients with acute non-dysenteric diarrhea between August, 2008 and July, 2009 in Shanghai, Hangzhou, Chongqing, and Tianjin, China. One step real-time RT-PCR was used for detection of norovirus (NoV) genogroups I and II (GI, GII). The NoV genotypes were classified based on partial capsid sequences. Rotavirus (RV) was detected in parallel. Among 4,123 fecal samples from outpatients, 1,067 (25.9%) were NoV-positive, of which 1,051 (98.5%) belonged to GII and 1,309 (31.7%) were RV-positive. In the inpatient group (n = 317), 25.6% were NoV-positive and 41.6% were RV-positive. Four hundred and fifty-one out of 1,067 NoV-positive strains were sequenced and genotyped and 6 typed strains were GI (3 GI.3, 2 GI.5, 1 GI.4) and 445 typed strains were GII. GII strains clustered into nine genotypes including GII.4 2006b (69.2%), the only GII.4 variant identified in this study, followed by GII.3 (23.8%), GII.6 (3.6%), GII.12 (1.3%), GII.2 (0.9%), GII.13 (0.4%), GII.14 (0.2%), GII.7 (0.2%), and GII.16 (0.2%). A peak of NoV infections was observed during the cold season in Tianjin, while NoV activity was higher between late summer and autumn and lower during winter in Shanghai, Hangzhou, and Chongqing. NoV is a common causative agent of childhood diarrhea in China and the seasons of NoV-associated diarrhea varies between regions. The results show that NoV GII.4 2006b was the predominant strain circulating in China between 2008 and 2009.