| Objective: To investigate the pathogenic characteristics of hand, foot and mouth disease (HFMD) in children in Hebei Province at the early period of prevalence and during prevalence, and to master and clarify the genetic characteristics of HFMD in order to provide scientific evidence for the prevention and control of HFMD.Methods:1 According to the prevalence condition of HFMD in 2009, six monitoring sites were established,including Shijiazhuang, Baoding, Xingtai, Tangshan, Langfang, Zhangjiakou.2 The subjects in the investigation were healthy children and children with HFMD. The specimens were collected at the early period of prevalence and during prevalence,3 The specimens were detected by Real Time RT-PCR, then the enteral virus(EV)-positive specimens were typed. The EV was isolated from EV -positive specimens in the children with HFMD.4 The sequencing primers in VP1 region of EV71 and CA16 were designed in order to be sequenced to perform nucleotide sequence homology analysis and construct the phylogenetic tree with DNASTAR software for analyzing the gene subtype and variation in Hebei province.5 Statistical software of SPSS13.0 was used to process and analyze the data.Results:1 In the study, 305 healthy children were enrolled.There were 157 healthy children and 148 healthy children at the early period of prevalence and during the prevalence, respectively. The 297 HFMD patients were enrolled to match with the healthy children, including 152 and 142 HFMD patients at the early period of prevalence and during the prevalence, respectively. 2 Fifty-four EV specimens were positive in 305 healthy children and the positive rate was 17.70%. The pathogens in healthy children were dominated by the other EV while EV71 and CA16 accounted for only little proportion. The 305 healthy children in accordance with the sampling time were divided into early period of prevalence group and prevalence duration group. Among the 157 healthy children in early period of prevalence group, 17 cases were positive, the positive rate was 10.83%. Among the 148 healthy children in prevalence duration group, 37 cases were positive, the positive rate was 25.00%. The results showed that the two periods were dominated both by the other EV that accounted for 64.71% and 91.89% among positive cases during early and prevalence duration, respectively. The EV positive rate in healthy children during prevalence was higher than that at early period of prevalence, however, the composition ratio was different. The order of EV positive rate in cities from high to low was Baoding(28.21%), Zhangjiakou(26.19%), Tangshan(22.50%),Xingtai(21.43%),Langfang(14.29%), Shijiazhuang(8.00%). The EV positive rate was higher during prevalence than that at early period of prevalence in Xingtai, Baoding and Tangshan. The sex and age had no effect on EV infection and HFMD pathogenic composition.3 There were 167 EV-positive cases among 297 HFMD patients and positive rate was 55.89%. The pathogens in HFMD patients were dominated by EV71. The other EV and CA16 were also detected, and the concurrent infection by EV71 and CA16 was found. The detection of 297 HFMD cases was performed according to the sampling time (two stages). At the early period of prevalence, 152 HFMD cases were detected, of which 79 cases were positive, and the positive rate was 51.97%. During the prevalence, 145 HFMD cases were detected, of which 88 cases were positive, and the positive rate was 60.69%. The EV positive detection rate was consistent in two stages, but the pathogenic composition was different. The composition ratios of CA16 and EV71 were higher at early period of prevalence, however, only the positive rate of EV71 was higher during prevalence.The order of EV positive rate in of the cities from high to low was Shijiazhuang (61.36%),Xingtai(60.98%), Tangshan(57.50%),Zhangjiakou(53.49%),Langfang(53.33%),Baoding(45.00%). The positive rate was higher during prevalence than that at early period of prevalence in Xingtai and Tangshan. The patients'sex and age had no effect on EV dection and HFMD pathogenic composition, which was similar to that in healthy children.4 The typing of the other EV: 16 cases of healthy children were further subtyped. Seven of them were typed who were all at prevalence duration. The two cases were CB5(from Baoding), one was CA6(from Baoding),four were ECO14(from Xingtai and Tangshan respectively).5 The results of virus isolation: 61 strains were isolated. There were 36 strains of EV71,18 strains of CA16,4 strains of CA10,2 strains of CA4 and 1 strain of CA9.6 The homogeneity of VP1 nucleotide and amino acids sequence of EV71 strains in Hebei Province was 94.7%~100.0% and 98.7~100.0%. These strains were quite different from representative strain of A and B genotype, but they were quite similar to C4 subgenome of C genotype. All the strains from provinces and cities nationwide and Hebei from 2009 to 2010 were C4a subtypes belong to the branch of C4.The homogeneity of VP1 nucleotide and amino acids sequence of CA16 strains in Hebei Province were 90.8%~98.9% and 99.0~100.0% respectively. These strains were quite different from representative strain of G-10 and Fuyang strain, which were quite closer to B1 subgenome of B genotype.7 The EV71 strains belonged to C4a evolution branch of C4 subgenotype, CA16 belonged to genotype B1a and B1b evolution branch of B1 by analyzing the EV71 and CA16 genetic characteristics and phylogenetic tree. But EV71 and CA16 genotypes were stable in Hebei province in recent years.Conclusion:1 EV carrying rate of healthy children is high at the monitoring points in 2010. The positive rate is higher during prevalence than that at early stage of prevalence. The pathogens are various in different periods and areas, but they are dominated by other EV, while EV71 and CA16 account little proportion. The CB5, CA6, ECO14 are also found in healthy children.2 EV carrying rate of HFMD cases do not have any change during prevalence. The pathogens are dominated by EV71 and CA16, while other EV accounts little proportion. But pathogen constitute ratio has a slight different at early period and during prevalence, and EV71 gradually takes the leading status.3 The children's gender and age do not have any effect on detection rate and pathogen constitution both in healthy and HFMD children.4 The results for analyzing EV71, CA16 gene show that EV71 strains belong to C4a evolution branch of C4 subgenotype, CA16 strains belong to genotype B1a and B1b evolution branch of B1.
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