Epidemiological And Etiological Characteristic Analysis Of Hand-foot-and Mouth Disease In Chongqing,2010-2013

Objectve: To understand the epidemiological characteristics andpathogen type of hand-foot-mouth disease (HFMD) in chongqing, in order toprovide evidence for the prevention and control strategics.Methods: Descriptive epidemiological methods were used to describethe epidemic characterstics of34841HFMD cases in Chongqing children’shospital from stool samples during2010to2013. Detection the pathogentype of830HFMD cases in hospital from with enterovirus VP1specificprimers by nRT-PCR, construct phylogenetic trees with the sequences toanalysis of the molecular characterstics.Results:1. There were two epidemic peaks every year for HFMD during2010to2013in Chongqing, of which one was from April to July and the other wasfrom October to December. The onset peak occurred mainly around the endof spring and summer in2010and2011, respectively56.02%and53.87%ofthe total number in annual cases; however, it occurred in winter in2012and2013, respectively42.91%and40.53%.94.27%of the patients were under5years old. The ratio of male to female cases was1.60:1. The major of thecases involved children residing separately from their parent (60.1%) andchildren in kindergarten (37.34%).2.(1)Among830stool samples, there were785samples with enterovrious infections, including58.47%with EV71,18.09%with CA16,3.18%with CA10,8.79%with CA6and8.79%with other enteric viruses andthere are2.68%cases are infection overlap.(2) EV71infection cases are themost in the second season of each year, while their percentage decrease inother seasons, and the percentage of Coxsackievirus increases. ForCoxsackievirus infection cases, they are mainly CA16infection in2010, andCA6are the major cases in2012and2013.(3) EV71infection cases are themost each year. The percentage of CA16infection cases decreased from31.23%in2010to4.67%in2013, while the percentage of CA6infectioncases increased from2.11%in2010to16.36%in2013.(4) In severe cases,EV71infection contributed the most, as high as74%in percentage.However,CA16cases decrease each year (from21.35%in2010to2.22%in2013). Inmild cases, EV71accounts for31.23%, and CA16infection came downform51.81%in2010to8.86%in2013, while CA6went up from4.3%in2010to35.44%in2013.(5) In the epiology spectra of serious illness casesand common cases, percentage of Coxsackievirus infection cases decreasedand percentage of EV71infection cases increased with the growing of theages of patients.3. Molecular epidemiology shows: EV71virus strain is the subtype ofC4a, and it has high homology with other typical stains in the mainland ofChina and other districts, and it has three branches. All CA16is subtype ofB1, with B1a and B1b prevailing by turn. And CA6and CA10strains havehigh homology with the recent typical strains in Spain and Finland.Conclusions: HFMD had seasonal prevalence in Chongqing from2010to2013, with two epidemic peaks each year. The onset peak was in thealternate of spring and summer in2010and2011and it happened in winterin2012and2013. The major of the cases involved children residingseparately from their parent and children in kindergarten, with the highest incidence of diseases for children under5years old. And the percentage ofthe cases for males is higher than females. The pathogens are mainly EV71,VA16, CA6and CA10, and the composit of them are change in differentperiods and seasons. EV71usually occurred in summer, whileCoxsackievirus mainly happened in winter, with the decreasing cases forCA16and increasing cases for VA6. For the serious illness cases, EV71infection cases are the most, and for common cases, EV71and CA16prevailed side by side. Analysis of Molecular evolution showed EV71strains in Chongqing are mainly subtype of C4a. All CA16strains aresubtype of B1, with B1a and B1b prevailing alternately. And CA6and CA10strains may have the same origin with other typical strain in the world.