一起甲型病毒性肝炎爆发的病原学特征分析

Etiological Characteristic Analysis on Hepatitis A in an Outbreak

目的了解一起甲型病毒性肝炎(甲肝)爆发流行株的病原学特征。方法收集全校338名学生(包括发病的16名学生)和18名教职员工血清,采用酶联免疫吸附试验(Enzyme-linked Immunosorbent Assay,ELISA)检测抗甲肝病毒抗体[Antibody to Hepatitis A Virus(HAV),Anti-HAV]IgM。选取8份病人和16份隐性感染者血清,用逆转录-聚合酶链反应(Reverse Transcription-Polymerase Chain Reaction,RT-PCR)扩增血清标本中的HAV核糖核酸(RibonucleicAcid,RNA)VP1-2A片段,测序结果利用脱氧核糖核酸Star软件进行比对分析。结果在356名调查者中,Anti-HAV IgM阳性感染者82例,阳性率为23.03%;其中学生81例,阳性率为23.96%,男性51例,女性30例;在教职员工中检出1例,阳性率为5.56%。在24份标本中检测HAV RNA阳性15份,其中甲肝病人标本6份,隐性感染者9份。选择5份标本进行VP1-2A基因片段序列测定,测序结果经过比对后发现,5株的VP1-2A序列完全一致。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%和100%;与中国其他地区流行株比较,核苷酸的同源性波动于92.3%～96.3%。与2004年宁波流行株的核苷酸和氨基酸的同源性分别是97.7%和98.3%。结论引起这起肝炎爆发疫情的病原是HAV,基因型为ⅠA亚型,在进化树上与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 To understand etiological characteristic and antigenic variation of Hepatitis A virus in an Outbreak in Ningbo in 2007.Methods 356 serum samples were collected.Anti-HAV IgM was detected by ELISA test.8 serum samples of patients and 16 serum samples of sub-clinical patients were selected to detect HAV RNA.VP1-2A nucleotide fragments from the samples were cloned by RT-PCR and sequenced.The sequence results were analyzed by DNA star software.Results AntiHAV IgM was detected from 82 samples,accounting for 23.03%.81 positive samples derived from 338 students,accounting for 23.96%.Among them,51 samples derived from male.Only one positive sample derived from staff.HAV RNA was detected from 15 serum samples.6 samples came from patients and 9 samples came from sub-clinical patients.VP1-2A nucleotide fragments from 5 samples were cloned and sequenced.The results showed that VP1-2A nucleotide fragments of 5 strains were identical.Comparing with various genotypes of HAV,Ningbo strains had the highest homology to AH2 nucleotide and amino acids of subtype IA strains（98% and 100% respectively）.Compared with other prevailing strains in China,its homology of nucleotide ranged from 92.3% to 96.3%.Compared with Ningbo prevailing strains in 2004,its homology of nucleotide and amino acids was 97.7% and 98.3% 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 strain AH2 but it was different evolutional branch from other prevailing strains in China.