Study on Pathogenic Features of Hand-Foot-Mouth Disease and Genetic Characteristics of EV71 Isolations in Chenzhou in 2011

Objective To understand the pathogenic features of hand-foot-mouth disease(HFMD) and the genetic characteristics of isolates of enterovirus 71(EV71) in Chenzhou in 2011,so as to provide basis for the prevention and control of HFMD.Methods The throat swab,anal swab or fecal were collected from HFMD cases in HFMD surveillance hospitals.Nucleic acid of EV71,coxsackievirus A 16(CA16) and other enterovirus were detected by real time fluorescent PCR.55 samples were randomly selected from EV71 positive ones for RD cell separation.VP1 fragment of EV71 was amplified from 10 isolations by reversed transcription-polymerase chain reaction(RT-PCR) for gene sequencing and sequence molecular phylogeny tree analysis.Results Totally,5,128 HFMD cases were reported in Chenzhou in 2011.Two peak time of incidence was found in May to July and November to December.Pathogenic analysis of 574 HFMD samples indicated that children aged 1 to 3 years were more likely to get infected,and the ratio of boys to girls was 2.04.Pathogens were identified in 461 out of 574 samples,with EV71,CA16,EV71+CA16 and other enterovirus accounting for 30.15%,31.89%,0.65% and 37.31%,respectively.HFMD caused by EV71,CA16 and other enterovirus differed in the distributions of the onset time,patient age and occurrence area(P0.001).Among 25 severe cases,EV71 was detected in 18 patients.And all of the 6 death cases were infected with EV71.Random detection of 68 samples with other enterovirus by real time PCR revealed that CA6(23 cases) and CA10(8 cases) accounted for 45.59%.Gene sequencing of 10 EV71 isolations illustrated that the genotype were all subgenotype C4a.The VP1 gene sequences of EV71 isolations from severe cases and common cases had small differences.Conclusions The occurrence of HFMD has obvious season,area,gender and age features.EV71 is the predominant pathogen of HFMD severe cases and death cases in Chenzhou in 2011.To prevent and control the rapid spread of HFMD,further study is desired on EV71 and the epidemic trend of non-EV71,non-CA16 entrovirus.