Molecular Epidemiology And Evolution Of Enterovirus Associated With Hand,Foot And Mouth Disease In China From 2008 To 2016

Hand,Foot and Mouth Disease(HFMD)is a common self-limiting infectious disease for children.Some severe infections can cause neurological complications and even death.Since the end of the 20 th century,there have been many outbreaks in Southeast Asia and the Pacific areas,such as Japan,Cambodia,Vietnam and other neighboring countries.In 2008,the first outbreak of HFMD in Fuyang City,Anhui Province,China,attracted great attention from the Chinese government.This disease was also listed as a national Class C notifiable infectious disease in the same year,when China set up the national monitoring system for Coxsackievirus A16(CVA16)and Enterovirus A71(EVA71).HFMD is mainly caused by a variety of enteroviruses(EV),of which EVA71 and CVA16 are the most important agents.Since 2008,more than one million children have been infected by HFMD every year in China.The molecular epidemiological characteristics of HFMD are constantly changing.In recent years,non-EVA71 and nonCVA16 enteroviruses has been increasing rapidly in prevalence,and they have become the main serotypes causing HFMD in some areas.However,the risk factors for HFMD,the genomic mutation characteristics associated with specific pathogenesis,and the comprehensive national molecular epidemiology and evolutionary history are still unclear.Therefore,I examined two aspects of the disease,one is the prevalence of HFMD in local cities and the other is the national enterovirus sequence,from which epidemiological characteristics of HFMD,the prevalence and evolution of enteroviruses,and the overall molecular epidemiologic profile of major enterovirus serotypes.To investigate the HFMD epidemic from 2008 to 2016 in Zhenjiang,China,a total of 37202 HFMD cases were investigated and 3707 nasopharyngeal swabs were detected for enterovirus infection using specific RT-quantitative PCR.We first reported a mixed pattern of HFMD seasonal epidemic with a combination of single-peak and two-peak patterns in alternate years,and the occurrence of sporadic and epidemic outbreaks of HFMD in kindergartens in Zhenjiang.We found that children younger than 4 years old were highly vulnerable to HFMD,and home children and boys had higher risk to develop severe HFMD than nursery children and girls.Among the detected samples,the prevalence of non-EVA71 and non-CVA16 enteroviruses showed a slight increasing trend from 2008 to 2016.This study first presents the dynamic of the HFMD epidemic in Zhenjiang from 2008 to 2016.In parallel,a total of 238 partial VP1 sequences were obtained,including 93 EVA71(39%),79 CAV16(33%),29 CVB3(12%),24 CVA6(10%),and 13 other enterovirus serotypes(5.5%).CVB3 is classified into seven genotypes A–G according to phylogenetic and distance analyses.All CVB3 strains from Zhenjiang belonged to genotype A.In contrast to other genotypes that are prevalent in Europe and other regions of China,and often associated with aseptic meningitis and myocarditis,CVB3 genotype A strains identified in Zhenjiang were only detected among HFMD patients.This high prevalence of CVB3 among HFMD children has never been reported,which might reveal a new epidemic trend of CVB3 among HFMD in China,and have epidemiological implications for monitoring the epidemic risk of CVB3.Finally,we performed systematic epidemiological and phylogenetic analyses of HFMD-related enteroviruses,and reported a rapidly increasing trend of other enteroviruses with a sharply decreasing trend of EVA71 prevalence in China from 2008-2016.In addition,we found that one subtype of each enterovirus was mainly responsible for the epidemic,and four genotypes EVA71_C4,CVA16_B1,CVA6_D and CVA10_C were the most predominant enterovirus strains and contributed to over 90% of all HFMD cases in China.The four major enterovirus genotypes showed different geographical and epidemiological profiles,and formed co-circulation with other genotypes,as well as other serotypes.The results suggest that more molecular epidemiological efforts should be focused on CVA16 and other enteroviruses and in some undeveloped areas.Furthermore,the epidemiological and evolutionary information of the four main enteroviruses have significant implications for virological surveillance,disease management and vaccine development,and provide scientific basis for policy-making on the prevention and control of HFMD.