Abstract: ObjectiveTo explore epidemiologic characteristics and influencing factors of severe hand-foot-mouth disease(HFMD) incidents in Ji'nan city from 2012 through 2013.MethodsAll severe HFMD cases diagnosed during the two years in Ji'nan city were surveyed with a questionnaire and the data collected were analyzed with unconditional logistic regression.ResultsAlmost all HFMD incidents under the age of 5 years were severe HFMD(496/520,95.38%) and the proportion of severe HFMD cases decreased with the increment of age among the HFMD cases(linear tendency:χ²=195.43,P<0.01) during the period.Of the severe HFMD cases,81.15%were scattered children,followed by preschool children(16.92%) and students(1.92%).The incidence of severe HFMD was significantly higher among the scattered children than among the residents of other age groups(χ²=123.24,P<0.01).The positive rate were 70.0%for enterovirus-71(EV71) among 120 severe HFMD cases with pathogenic detections of stool,throat swab,cerebrospinal fluid specimens.Multivariate logistic regression analysis showed that the risk factors of severe HFMD incident included age,delay in seeking medical treatment,fever,oral ulcer,skin rash,and positive to EV71,with the odds ratios of 4.35,1.43,2.54,1.96,3.78,and 19.65,respectively,(all P<0.05).ConclusionThe incidence rate of severe HFMD in Ji'nan city is high;EV71 is the main pathogen related to the severe HFMD incidents and small children is the key population for the control of severe HFMD incidents.