[Epidemiological surveillance of norovirus and rotavirus diarrhea among outpatient children in five metropolitan cities].

OBJECTIVE To survey the clinical epidemiological features of norovirus and rotavirus diarrhea among children living in 5 cities. METHOD A prospective epidemiological investigation was conducted among outpatient children with acute diarrhea between August 2008 and July 2009 in Shanghai, Hangzhou, Guangzhou, Chongqing and Tianjin. The stool samples were randomly collected from children with non-dysentery diarrhea. Group A rotavirus antigen was tested by the kit that applies colloidal gold method in all specimens. GI and GII genogroups of norovirus were detected by one-step real-time reverse-transcription polymerase chain reaction (RT-PCR). The detection rates, seasonality and susceptible age of both viruses-associated diarrhea were analyzed. RESULT During the one-year period, 5091 fecal samples were obtained, of which 1563 (30.7%) were rotavirus-positive. The detection rates of rotavirus were 29.5% (268/916) in Shanghai, 36.1% (334/926) in Hangzhou, 26.3% (254/968) in Guangzhou, 34.1% (359/1054) in Chongqing and 28.2% (348/1233) in Tianjin, respectively. Among the remaining 3528 rotavirus-negative samples, 1049 (29.7%) were identified to be norovirus-positive. The detection rates of norovirus were 21.2%(136/642) in Shanghai, 31.3% (185/592) in Hangzhou, 24.2% (173/714) in Guangzhou, 31.8% (221/695) in Chongqing and 37.7% (334/885) in Tianjin, respectively. It is estimated that the infection rate of norovirus among outpatients with acute diarrhea is at least more than 20.6% (1049/5092). Of 1049 norovirus strains, 1036 (98.7%) were GII genogroup and 16 (1.5%) were GI genogroup, 3 were mixed with GI and GII genogroups. The 1049 children with norovirus diarrhea aged between 1 month and 14 years with the median age of 10 months (mean: 13.9 ± 16.9 months) and 91.8% were 2 years old or younger. The 1563 children with rotavirus diarrhea aged between 1 month and 11.3 years with the median age of 10 months (mean: 12.9 ± 13.7 months) and 92.5% were 2 years old or younger. The median ages between norovirus-infected children and rotavirus-infected children were significantly different (P < 0.05). The peak seasons of rotavirus diarrhea spanned autumn and winter (from October to February). The peak seasons of norovirus diarrhea presented in the winter and spring (from November to April) in Tianjin. Norovirus became active in April and usually predominantly prevalent in the summer and autumn (from July to October) in Shanghai, Hangzhou and Chongqing. However, norovirus was sporadically prevalent in the spring and detected more commonly in the other seasons in Guangzhou. CONCLUSION Both rotavirus and norovirus are the major causative agents for childhood diarrhea. The seasonality of rotavirus diarrhea was similar among the 5 cities. Nevertheless, the seasonality of norovirus diarrhea was diverse in the different areas. In Tianjin located in the north of China, norovirus was quite prevalent in the cold season. In the east (Shanghai and Hangzhou) and south-west (Chongqing), norovirus prevailed dominantly in the summer and autumn. In the south (Guangzhou), the activity of norovirus was more obvious in the summer, autumn and winter.