[Trend of epidemics and variation of pathogens of hand, foot and mouth disease in China: a dynamic series analysis, 2008-2017].

Objective: To understand the trend of epidemics and variation of pathogens on hand, foot and mouth diseases (HFMD) in China for setting up appropriate intervention measures.
Methods: Data related to reported cases and outbreaks of HFMD from the National Notifiable Disease Surveillance Reporting System of China, 2008 to 2017, was collected and analyzed. Based on the geographical location and types of climate, the total 31 provinces, autonomous regions and municipalities in the mainland of China, were divided into seven regions: north-west, north, mid-north, east, mid-south, south, and south-west regions, with epidemic trends and variation of pathogens analyzed. The average speed of growth on the dynamic series from 2008 to 2017 was calculated, using the Geometric Average method.
Results: The overall reported incidence rate of HFMD during 2008-2017 was 134.59 per 100 000 population with an average increase of 15.92%. The proportion of severe cases was 0.84%, with 9.56% increase. The reported mortality rate of HFMD was 0.03/100 000, with an average decrease of 3.49%. The case fatality rate was 0.02% and with a decrease of 16.86%. A total of 6 000 outbreaks were reported during the decade. Except for 1.09% decrease on the incidence rate in the north region, all the other regions showed an increase on the morbidity rates, with the highest as25.20% in the south region. Mortality rates showed 27.53% and 0.60% increases in both the south-west and mid-north regions, respectively. Mortality rates in the other regions all showed a decreasing trend. In terms of case fatality rate, it increased 4.15% in the south-west region while all decreased in the other regions. Two higher age-special morbidity rates appeared in the 1 year olds as 3 184.19/100 000 and in the 2 year olds as 2 547.47/100 000, with the most increase seen in both 0 year (26.08%) and 1 year age groups (23.35%). High age-specific mortality rates were noticed in both the 1-year group as 0.86/100 000 and the 2-year group as 0.54/100 000, however with reductions as 1.21% and 10.70% respectively. As for the case fatalities, the 0 year olds and 1 year olds accounted for 0.039% and 0.027% but both of them had decreased by 19.12% and 19.91%, respectively. Case fatality rates decreased by 16.93% and 16.75%, in males and females. Proportions of EV71 and Cox A16 decreased by 4.28% and 3.07%, but the proportion of other entero-viruses increased by 16.07%. EV71 was responsible for the high frequency of epidemics in both mid-north and the mid-south regions. However, in other five regions, other strains of EV's were responsible for the epidemics. Conclusions: The characteristics of HFMD in China showed that the morbidity of HFMD and proportion of severe cases were both in increasing trends but both the mortality and case fatality of HFMD were decreasing. Children younger than 3 years old showed both high infection and death rates for HFMD. Epidemics caused by other enteroviruses of non-EV71 and non-Cox A16 were seen more. Variance and pathogens related to the epidemic cycles appeared different in the seven regions.