Surveillance on the epidemiological and etiological characteristics of hand-foot-mouth disease during the outbreaks in three cities of Jiangsu province, 2012-2015

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Objective: To analyze the epidemiological and etiological characteristics through monitoring the outbreaks of hand-foot-mouth disease (HFMD), in three cities of Jiangsu province from 2012 to 2015 and to provide evidence for prevention and control of the disease. Methods: Data related to cases of HFMD during the outbreaks was collected through active surveillance programs in three cities of Jiangsu province, under the guidelines of clusters and outbreaks of HFMD (2012 edition HFMD). Features related to clusters and outbreaks of the disease were identified according to the real-time RT-PCR detection. Descriptive analysis was conducted to understand the type/subtype of HFMD virus and time, area, place and extent of the outbreaks. Logistic regression was used to explore the influencing factors. Results: From 2012 to 2015, a total of 1 425 HFMD epidemics, including 1 314 clusters and 111 outbreaks were reported. Two incidence peaks were observed each year, between March and June, as well as between September and December, accounting for 58.18% (829/1 425), 33.68% (480/1 425), respectively. Most HFMD clusters and outbreaks were reported in Wuxi city, accounting for 59.30% (845/1 425) of the total. Most HFMD clusters and outbreaks happened in kindergartens, accounting for 68.63% (978/1 425) of the total. A total of 931 HFMD clusters and outbreaks were confirmed under laboratory findings. The main pathogens were Entervirus type 71 (EV71) in 2013 and Coxsackie A16 (Cox A16) in 2015, respectively, while both EV71 and Cox A16 were predominant in 2012 and 2014. With multivariate backward conditional regression, surrounding environment was identified as important risk factor associated with the attack rate. Health condition of the environment was quite good, with low attack rates (middle vs. bad: OR=0.150, 95% CI: 0.034-0.667; good vs. bad: OR=0.072, 95%CI: 0.016-0.317). Time between the onset of index patient and the reporting of HFMD clusters or outbreaks was important in the control program of HFMD epidemics (4-7 d vs. 1-3 d: OR=3.452, 95%CI: 2.293-5.198; 8 d vs. 1-3 d: OR=12.108, 95%CI: 7.767-18.763). Conclusions: The clusters and outbreaks of HFMD happened in Jiangsu province showed an obvious feature of seasonality. The predominant types or subtypes of the virus varied in different years. Kindergartens were the hard-hit places of HFMD clusters and outbreaks. Timely report of the disease appeared the key point regarding the control of HFMD clusters and outbreaks.