[Investigation of human calicivirus (HuCV) diarrhea among infantile and young children in China, 1999--2005].

Human calicivirus (HuCV) has been well known as an important pathogen of outbreak and sporadic acute nonbacterial gastroenteritis worldwide. To investigate epidemiological feature and genetic diversity of HuCV among children in China, fecal specimens were collected from children under 5 years of age with acute diarrhea at 13 hospitals in different provinces across China. The study was performed year-round from January 1999 to June 2005. Fecal specimens were tested for bacteria and rotavirus first and the negative specimens then were tested for HuCV using ELISA and RT-PCR. PCR amplicons were cloned and sequenced for strain characterization. A total of 4426 rotavirus- negative fecal samples were screened. From these, 840 (19%) were positive for HuCV by either or both ELISA (14%) and RT-PCR (9.6%). HuCV infection occurred year-round with an epidemic in each winter (October-January) and mainly in children at 6 -- 17 months of age. Of 151 HuCV strains characterized, 146 belong to norovirus (NV, 96.7%) and 5 were sapoviruses (SV). Among norovirus strains, genotype GG II/4 was most common (99/146), followed by GG II/3 (22/146), GG II/5 (8/146), and 2 strains of each of GG II/6, GG II/7, GG II/8, and GG I/2, the other 9 strains of NV GG II were unique, potentially belonging to new genotypes. These results plus the epidemiology data suggested that HuCVs are an important cause of severe diarrhea in Chinese children that were under reported due to a lack of a simple diagnostic assay. The finding of the potential new genotypes indicates that the current assays need to be improved for broader detection and besides, a continual surveillance for better understanding the epidemiology the disease burden and the searching for new strains of HuCVs is necessary.