Genetic characteristics of breakthrough varicella-zoster virus infection during the varicella outbreaks in Minhang District of Shanghai

Objective To analyze the genetic characteristics of breakthrough varicella-zoster virus infection during the varicella outbreaks in Minhang District of Shanghai in 2013-2014. Methods Samples of the varicella-zoster liquid were collected from patients with chickenpox in Minhang District in 2013-2014 and used for the extraction of genomic DNA. The open reading frame (ORF) of 22 and 62 regions were sequenced and further analyzed by using bioinformatics methods. Results A total of 24 samples were successfully collected and sequenced, and all of them were wild strains. Among the 24 varicella-zoster virus strains, 23 strains were highly homologous to the parental strain (P-Oka) and the vaccine strain (V-Oka), indicating that they belonged to J genotype. Only one strain, whose genotype was between M and E, was highly homologous to the mosaic(M)CA123 strain (M1 genotype), indicating that it might belong to M1 genotype. Conclusion The epidemic strains of varicella-zoster virus in Minhang District were mainly J genotype. Local epidemic of M and other genotypes of varicella-zoster virus also existed. There were some gene variations in different strains of J genotype. These varicella-zoster virus strains of non-vaccine genotypes might be one of the reasons causing the breakthrough cases of chicken pox. Key words: Varicella-zoster virus; Breakthrough case; Varicella outbreak; Genetic characteristics; Bioinformatics