目的 查明引起2004年宁波局部地区甲型病毒性肝炎（甲肝）暴发疫情的病原并分析其基因特征。 方法 用酶联免疫吸附试验检测血清中的甲肝病毒IgM抗体（HAV IgM）和戊型肝炎病毒IgM抗体（HEV IgM），利用逆转录-聚合酶链反应（RT PCR）检测粪便样品中的HAV核酸（RNA）并扩增VP1基因，测序结果利用DNA star软件进行比对分析。 结果 172份血清样品中HAV IgM均为阳性，HEV IgM均为阴性。172份粪便样品中共检测到HAV RNA阳性样品74份，占43.0%。选择5份样品进行HAV VP1基因扩增并测序，测序结果经过比对后发现4株宁波株(NB2004-10、NB2004-11、 NB2004-51和 NB2004-71)的VP1基因是完全一致的；NB2004-75与以上4株的核苷酸的同源性为99.9％，氨基酸的同源性为99.7％；宁波株与HAV各基因型标准株比较， 与IA亚型毒株AH2的核苷酸和氨基酸的同源性最高， 分别为98.9％和99.7%～100.0％；与中国其他地区流行株比较，核苷酸和氨基酸的同源性波动于89.4%～96.7%和97.0％~100.0％。结论 引起这次肝炎暴发疫情的病原是甲肝病毒，其基因型为IA亚型，与日本株AH2、AH3亲缘关系最近，与中国其他地区流行株处于不同的进化簇上。
Objective The study was conducted to identify the pathogens causing a local outbreak of hepatitis A in Ningbo in 2004 and analyze its gene characteristics. Methods HAV IgM and HEV IgM of serum samples were detected by using ELISA test; HAV RNA in stool samples was detected by RT PCR; VP1 gene of HAV was cloned by RT PCR and sequenced; the sequence results were analysed by DNAstar. Results All 172 serum samples were positive for HAV IgM and negative for HEV IgM, and HAV RNA was detected from 74 stool samples, accounting for 43.0%. The HAV VP1 genes of five samples were cloned and sequenced, the results of which suggested that the VP1 genes of 4 strains (NB2004-10, NB2004-11, NB2004-51 and NB2004-71) were identical, and the nucleotide homology between NB2004-75 and these 4 strains was 99.9%, and the amino acid homology was 99.7%. Comparing with various genotypes of HAV, Ningbo strains had the highest homology to AH2 nucleotide and amino acids of subtype IA strains, (98.9% and 99.7%-100.0%, respectively). Compared with other prevailing strains in China, its homology of nucleotide and amino acid ranged from 89.4% to 96.7% and from 97.0% to 100.0%, respectively. Conclusion The pathogen that caused this outbreak was hepatitis A virus; the genotype of the strains was serotype IA, which had the closest homology to Japanese strains AH2 and AH3 but was of a different evolutional branch from other prevailing strains in China.