Etiological Surveillance Of HFMD And Survey On The Enterovirus Distribution In Healthy Person

Hand-foot-mouth disease (HFMD) is a common disease which is benign andself-limiting among children, but severe HFMD with complications are also developed.In the past decade, the size and frequency of HFMD outbreaks have greatly increased inChina and it has become an important public health issue. Concerning the currentcomplex situations for prevention and control of HFMD, the research was conducted intwo areas:On one hand, in mainland China, the surveillance on HFMD was mostly focused onEV71and CVA16, while the information on the pathogenic role of other enteroviruses,their epidemiological and genetic characterization are still lacking. So a hospital basedsurveillance was performed on HFMD in three heavily inflicted regions from March2009to July2013. We have herein broadened these analyses to include more regionsand over a longer time span in order to provide a more comprehensive overview of theviral pathogens of HFMD, as well as their epidemiological, clinical and geneticcharacteristics. The results showed a total of2308children were recruited in the studyand91.00%of samples were detected positive for enterovirus, with the frequentlypresented serotypes as EV71(1311,56.80%) and CVA16(502,21.75%). CVA6andCVA10were detected as sole pathogen in81(3.51%) and105(4.55%) cases,respectively. Besides, there were still remain19enterovirus serotypes could causeHFMD. The risk factors for severe HFMD were evaluated based on the multivariatelogistic analysis, and the lower age (≤2years old: OR=1.867,95%CI:1.317-2.646;2-4 years old: OR=2.028，95%CI:1.417-2.902) and EV71infection (OR=2.900,95%CI:2.052-4.100) were independently associated with higher risk of severe HFMD. Theanalysis of molecular epidemiology indicated that the sequences of EV71wereconserved and less variant. Furthermore, EV71C4a cluster is still the predominant virusin China. CVA16phylogenic analysis of the whole VP1coding sequences showed thatall the CVA16strains in our study belonged to the B1a and B1b cluster. The strainswere closely related to strains identified in Vietnam, Australia and Japan which wereco-circulate together with China. CVA6and CVA10both formed with obviousgeographical distribution pattern.On the other hand, most of previous data on enterovirus circulation have been reportedfrom the analysis of specimens from patients, whereas little epidemiologic informationis available for the enterovirus circulation in healthy population, especially in China. Toaddress this issue, we conducted a case-control study that included throat samples from579children with HFMD and from254healthy controls from May2010to October2010. Throat samples from49households (98parents and53healthy children) werealso analyzed. Phylogenetic analysis was carried out to study genetic relationships ofEV71strains, and the results showed the positive rate of enterovirus in HFMD patientswas significantly higher than that in healthy controls (76.0%vs.23.2%, P<0.001). TheEV71(43.7%vs.15.0%, P<0.001), CVA16(18.0%vs.2.8%, P<0.001), and CVA10(5.7%vs.0.8%, P=0.001) serotypes were significantly overrepresented in HFMDpatients in comparison to healthy children. Other enterovirus serotypes were detectedwith comparable frequency in cases and controls. Among49households,22households(44.9%) had at least1family member positive for enterovirus. Children hadsignificantly higher enterovirus positive rate than adult (28.3%vs.14.3%, P=0.037).The enterovirus positive rate was similar between mothers and fathers (12.24%vs.16.32%, P=0.56). The VP1sequences of EV71from HFMD patients and healthy children were nearly identical and all were clustered in the same clade, C4a.In summary, our study demonstrated the varieties of enterovirus genotypes in thepathogens of HFMD based on a comprehensive surveillance in China. CVA6andCVA10were co-circulating with EV71and CVA16. And we also analyzed theirepidemiological, clinical and genetic characteristics of the four enterovirus serotypes.On the other hand, the co-circulation of multiple enterovirus serotypes in healthypopulation was also demonstrated during epidemic. Our study deserves the publicattention on HFMD control.