Figure 2From: Epidemiology of norovirus infections among diarrhea outpatients in a diarrhea surveillance system in Shanghai, China: a cross-sectional studyAge distribution of NoV(+), NoV(−), RV(+) and bacteria patients. From May 2012 to September 2012, only 6 sentinels were under surveillance. A child sentinel joined in October 2012. In August 2013, the number of sentinels expanded to 23.Back to article page