Epidemiological characteristics of hand, foot, and mouth disease in Shandong, China, 2009-2016

Abstract

In the past decade, hand, foot, and mouth disease (HFMD) has posed a serious threat to childhood health in China; however, no epidemiological data from large HFMD epidemics have been described since 2013. In the present study, we described the epidemiological patterns of HFMD in Shandong province during 2009-2016 from a large number of symptomatic cases (n = 839,483), including >370,000 HFMD cases since 2013. Our results revealed that HFMD activity has remained at a high level and continued to cause annual epidemics in Shandong province from 2013 onwards. Although the incidence rate was significantly higher in urban areas than in rural areas, no significantly higher case-severity and case-fatality rates were found in urban areas. Furthermore, the seventeen cities of Shandong province could be classified into three distinct epidemiological groups according to the different peak times from southwest (inland) to northeast (coastal) regions. Notably, a replacement of the predominant HFMD circulating agent was seen and non-EVA71/Coxsackievirus A16 enteroviruses became dominant in 2013 and 2015, causing approximately 30% of the severe cases. Our study sheds light on the latest epidemiological characteristics of HFMD in Shandong province and should prove helpful for the prevention and control of the disease in Shandong and elsewhere.

Figure 1

Sex distribution and clinical severity of overall cases of HFMD in Shandong province, 2009–2016. (A) Sex distribution of probable and laboratory-confirmed cases. (B) Sex distribution of severe cases.

Figure 2

Estimated average incidence rates, case-severity risk and case-fatality ratesof all HFMD cases in 17 cities of Shandong province, 2009–2016. (A) Geographic distribution of average incidence rates of probable and laboratory-confirmed cases. (B) Geographic distribution of average case-severity risk of probable and laboratory-confirmed cases. (C) Geographic distribution of average case-fatality rates of probable and laboratory-confirmed cases.

Figure 3

Proportion of enterovirus serotypes in laboratory-confirmed cases of HFMD by clinical severity in Shandong province, 2009–2016. (A) Based on all the probable and laboratory-confirmed cases. (B) Based on mild cases. (C) Based on severe cases. (D) Based on fatal cases.

Figure 4

Heatmap of surveillance data for HFMD by city and HFMD epidemiological region, 2009–2016. (A) HFMD epidemic curve based on the number of weekly reported cases. (B) Time series of weekly reported cases of HFMD standardized by the number of annual cases. The cities were ordered by longitude from the westernmost (top) to the easternmost (bottom). (C) Clustering analysis of seasonal distribution of HFMD cases, plotted as the median value of proportion of cases in each week of the year from 2009 to 2016. (D) Classification of the epidemiological regions by clustering analysis.