Chickenpox cases monitoring and epidemic strains gene polymorphism analysis in Ningbo, Zhejiang

Abstract

Objective To analyze the varicella-zoster virus (VZV) epidemiology and the genotype characteristics of epidemic strains in Ningbo from 2009 to 2011.Methods The incidence data of chickenpox cases from Ningbo public health emergency report management system were collected and analyzed.Some vesicle fluid samples from chickenpox cases were collected.The VZV epidemic strains were genotyped by PCR method and the epidemic strains were identified by the restriction enyme Sma Ⅰ.The VZV virus was isolated by MRC-5 cells.Results The reported incidence rates of chickenpox in Ningbo were 23.33/100 000,26.24/100 000 and 36.25/100 000 from 2009 to 2011.Children aged 7-12 years had the highest incidence rate (245.21/100 000).Two seasonal peaks of chickenpox incidence were from May to June and November to December,respectively.The PCR detection result of VZV from 32 vesicle fluid samples showed that 25 samples were positive.Genotype results showed 2 kinds of different genetic types of strain:2 samples were M1 type strains,and the other 23 samples were J type strains.Conclusions Ningbo chickenpox cases mainly occur in late spring to early summer and late autumn to early winter,with the school-age children aged 7-12 years as the main patients.J strains are the major epidemic swain,but also have the local popular Ml type strain. Key words: Chickenpox; Epidemiological analysis ; Herpesvirus 3, human; Genotypes