| Objectives: A epidemiological study on common diarrheal viruses was conducted in Lanzhou, China, 2006-2007, to provide the theory evidence for prevention and treatment to virus diarrhea. The present study also aimed to study the prevalence of human bocavirus(HBoV) in Lanzhou, China, and to clarify whether it plays a causative role in diarrhea or not.Methods: 1. In the first hospital of Lanzhou university from Jul 2006 to Jun 2007, we collected 286 stool specimens from children hospitalized with diarrhea and 98 asymptomatic controls. Rotavirus was detected by ELISA, further strain characterization was carried out by nested PCR. The norovirus genotypes GI and GII, sapovirus, astrovirus, adenovirus and group B,C rotavirus were detected by RT- multiplex PCR and PCR, and the positive specimens were characterized by nucleotide sequencing.2. We also conducted a case-control study that examined stool samples from 397 children hospitalized with diarrhea and 115 asymptomatic controls from Jul 2006 to Sep 2007. HBoV was detected using the polymerase chain reaction (PCR). Real-time PCR was used to quantify the viral loads in case and control groups.Results: 1. At least one of the four viral agents was found in 64.0% (183/286) of the specimens. Rotavirus, human calicivirus, astrovirus, and adenovirus were identified in 47.6% (136/286) , 15.0% (43/286) , 3.8%(11/286), and 1.4%(4/286) of 286 specimens respectively. Rotavirus G1 (64.7%)was the most prevailing serotype, followed by G3 (15.4%). Within the P genotype, P [8] (68.4%) was the most common genotype, P[6] strain(2.9%) was detected for the first time in this area. The most common G-P combination was G1P [8] (48.5%). The percentage of human calicivirus increased distinctly in this year, norovirus GII /4 (74.4%) was the leading strains, and all of these were the subtype of variant 2006b strain, which was the main cause of some outbreaks globally from 2006. All astrovirus belonged to genotype 1. Adenovinis belonged to two distinct subgenera (C, and F) with three serotypes (Ad5, Ad40, and Ad41). Nother group B nor C rotavinis was detected. 11 of 286 (3.8%) samples were found positive with two viral agents, in which 6 samples contained both group A rotavinis and astrovirus, and 5 samples contained both group A rotavirus and human calicivirus. In the 98 control samples, 3 rotavirus, lnorovirus and 1 astrovirus were detected, and their serotype and genotype were coincident with that in the case group.2. Of the 397 cases, HBoV was detected in 14 samples, and nine were co-infected with either rotavirus (7/14) or human calicivirus (HuCV) (2/14). Many (57.1%; 8/14) of the HBoV infections occurred during September-December 2006. Most (12/14) of the HBoV-infected children were 7-18 months old. The percentage of HBoV did not differ significantly between cases and controls (3.5 vs. 3.5%), and the statistical analysis did not support a correlation between HBoV and more severe clinical symptoms. The viral load differences of the two groups were not significant (lognormal t-test, P=0.09). In addition, the VP1/VP2 partial gene of HBoV from cases and controls showed minimal sequence variation.Conclusion: 1. The results indicated clearly the impact of viral agents causing diarrhea and the importance of long-term systematic surveillance. Rotavirus was also the most important pathogen, but the human calicivirus should be given more attention.2. A single genetic lineage of HBoV was revealed in human subjects in China. Despite its high prevalence in stool samples, our study does not support a causative role of HBoV in diarrhea. HBoV may be an innocent bystander rather than a causative agent in diarrhea.
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