Etiological analysis of an epidemic of viral diarrhea among newborn infants

Objective　The study was conducted to identify the etiological agent that induced an epidemic of neonatal viral diarrhea and to analyze its molecular biological characteristics. Methods The rotavirus antigen was detected by dot- immunogold filtration assay, adenovirus by latex agglutination test, rotavirus nucleic acid in stool samples by polyacrylamide gel electrophoresis (PAGE), and enterovirus by RT-PCR. The VP7 gene of rotavirus was cloned and sequenced by RT-PCR, the results of which were analyzed by DNAstar and Blast. Results　Rotavirus was detected in nine out of eleven samples by dot-immunogold filtration assay, the positive rate being 81.82%. Both adenovirus and enterovirus detection were negative. Ten samples were positive for rotavirus detected by PAGE, as eight of them manifested a 4-2-3-2 electrophoresis band, the positive rate being 72.73%. However, the other two positive samples showed distinctively different bands. The VP7 gene could be cloned from the eight samples that had 4-2-3-2 bands by RT-PCR, and three of them were then used for gene sequencing. Sequence analysis revealed that the nucleotide homology of VP7 gene between the three strains was 99.90%, and the amino acid homology was 100％; the VP7 nucleotide homology of them with the serotype G1 standard strain Wa was 91.30％-91.50％, and amino acid homology of VP7 gene 94.80％. Therefore, they had the closest genetic relationship with the Thai-2104 strains, and they were in a different evolutionary branch that separated themselves from the other strains that used to cause epidemics in China. Conclusion　It was human rotavirus A that caused the epidemic of neonatal viral diarrhea. The primary banding type of this pathogen, serovar G1, was 4-2-3-2.