Epidemiological characteristics
Demographic characteristics
A total of 19,512 HFMD cases were reported in Zhengzhou Children's Hospital, including 237 severe cases and 2 deaths in 2016. The highest monthly incidence is between May and July (see Tab.1). The majority of HFMD cases are in the 0-5 year age group (96.97%, 18920 cases) in Fig.2. Most patients with HFMD are scattered children (75.5%) or kindergarten preschool children (22.9%). The remaining cases (1.6%) are students and adults. In the analysis of 290 laboratory genotyped cases, the proportions of cases infected by Cox A16, EV71 and other enterovirus infections are 8.28%, 57.93% and 33.79%, respectively. Therefore, the main causative viruses are EV71 and other enteroviruses, which is different from the previous work by Wang's group [7].
Among all HFMD cases, 11,823 were male and 7,689 were female. The gender ratio (male/female) was 1.54. The 0-5 year age group had the highest incidence of HFMD in 2016. The time of onset of HFMD cases varied among different age groups, but the difference was not significant (Tab.2), and the 0-5 age group had the highest incidence in May (4563, 23.4%), while the incidence cases reached their lowest value in February (0.7%). Among them, the incidence of the age group of >14 years old only appeared in July and September. In addition, the gender ratio of HFMD cases also varied among different age groups (in Tab.3). For the 0-14 year age group, male patients with HMFD are generally higher than female patients. However, for the >14 age group, all HFMD patients are male. Overall, the incidence of HFMD is significantly higher in male than in female, which is consistent with previous reports [7]. In Fig.3, the result showed that the incidence of HFMD cases showed obvious seasonal distribution, with the peak incidence in 2016 occurring in summer (between April and July).
Table 2
Monthly HFMD incidence and seasonal analysis among different age groups.
Month
|
Age(year)
|
Number
|
2016
|
|
|
Jan
|
0-5
|
298
|
|
6-14
|
8
|
|
>14
|
0
|
Total
|
|
306
|
Feb
|
0-5
|
145
|
|
6-14
|
7
|
|
>14
|
0
|
Total
|
|
152
|
Mar
|
0-5
|
478
|
|
6-14
|
8
|
|
>14
|
0
|
Total
|
|
486
|
Apr
|
0-5
|
2195
|
|
6-14
|
48
|
|
>14
|
0
|
Total
|
|
2243
|
May
|
0-5
|
4563
|
|
6-14
|
181
|
|
>14
|
0
|
Total
|
|
4744
|
Jun
|
0-5
|
3637
|
|
6-14
|
119
|
|
>14
|
0
|
Total
|
|
3756
|
Jul
|
0-5
|
2291
|
|
6-14
|
77
|
|
>14
|
3
|
Total
|
|
2371
|
Aug
|
0-5
|
1726
|
|
6-14
|
48
|
|
>14
|
0
|
Total
|
|
1774
|
Sep
|
0-5
|
1286
|
|
6-14
|
36
|
|
>14
|
1
|
Total
|
|
1323
|
Oct
|
0-5
|
872
|
|
6-14
|
23
|
|
>14
|
0
|
Total
|
|
895
|
Nov
|
0-5
|
948
|
|
6-14
|
23
|
|
>14
|
0
|
Total
|
|
971
|
Dec
|
0-5
|
458
|
|
6-14
|
10
|
|
>14
|
0
|
Total
|
|
468
|
2015
|
|
|
Dec
|
0-5
|
22
|
|
6-14
|
1
|
|
>14
|
0
|
Total
|
|
23
|
Table 3
Gender difference analysis of HFMD cases among different age groups.
Age
|
Male(n)
|
Female(n)
|
0-2
|
7846
|
5330
|
3-5
|
3167
|
2130
|
6-14
|
359
|
230
|
>14
|
4
|
0
|
Demographic characteristics
In 2016, the HFMD patients in Henan Province were mainly distributed in Zhengzhou, Xuchang, and Xinxiang, among which Zhengzhou accounted for the highest proportion, reaching about 87%. Figure 4 shows the distribution of HFMD incidence in Henan Province. From Figure 4, we can see that the high incidence area of HFMD in 2016 was mainly concentrated in the center of Zhengzhou, and the epidemic spread radially and quickly spread to the whole province, especially the northern regions. The incidence of
Table 4
The regional autocorrelation analysis of HFMD in Zhengzhou city, Henan Province
Location
|
Number
|
Percentage (%)
|
Zhongyuan district
|
1504
|
8.87%
|
Erqi district
|
1050
|
6.18%
|
Jinshui district
|
5474
|
32.27%
|
Huiji district
|
1571
|
9.26%
|
Guancheng district
|
1348
|
7.95%
|
Shangjie district
|
67
|
0.39%
|
Gongyi country
|
39
|
0.23%
|
Xinzheng country
|
588
|
3.46%
|
Dengfeng country
|
47
|
0.28%
|
Xinmi country
|
397
|
2.34%
|
Xingyang country
|
386
|
2.28%
|
Zhongmu country
|
781
|
4.6%
|
Jishukaifa district
|
1249
|
7.35%
|
Zhengdong district
|
2335
|
13.76%
|
Hangkonggang district
|
279
|
1.64%
|
Others
|
438
|
2.58%
|
Total
|
16965
|
100%
|
the southeastern regions was lower, especially in Xinxiang, Shangqiu and Zhoukou areas. In addition, there were also significant differences in the incidence of HFMD between provincial cities (Table 4). A Local Indicators of Spatial Association (LISA) analysis of the incidence of HFMD in 2016 identified distinct patterns of spatial associations in the prevalence of HFMD (Figure 5). High-High and Low-Low modes indicate clusters of similar values for HFMD incidence, while Low-High and High-Low indicate spatial outliers. The results in Figure 5 showed that the incidence of HFMD in urban and rural areas in northern Zhengzhou has a High-High positive spatial autocorrelation, while the incidence of HFMD in urban and rural areas in northwestern Zhengzhou has a stable Low-Low positive spatial autocorrelation. The towns with negative spatial associations are mainly distributed in the south and northeast of Zhengzhou.
Analysis of HMFD cases after EV71 vaccination
Since the second half of 2016, we have implemented vaccination against hand, foot and mouth disease for residents in Henan. In this study, we conducted a comparative analysis of HFMD cases before and after vaccination, and the detailed data are recorded in Table 5. The results of this study showed that the total number of HFMD patients decreased one year after vaccination, and the proportion of EV71 positive patients decreased from 0.86% to 0.28%. After 2 years of EV71 vaccination, EV71-positive patients were fully controlled, achieving complete clearance. In the third year of vaccination, the total number of HFMD infections continued to decline, but a small number of EV71-positive patients appeared. This result showed that EV71 vaccination is time-sensitive. Certainly, this result may also be due to the fact that the number of cases collected by Zhengzhou Children’s Hospital is not comprehensive enough, resulting in deviations in the experimental results. In addition, in this work, we found that after the EV71 vaccine, the number of severe patients and death cases also decreased. Therefore, EV71 vaccination can effectively prevent and control HFMD, and can reduce the cases of severe patients and death cases.
Table 5
Analysis of HFMD cases before and after EV71 vaccination.
Year
|
Number of HFMD
|
Severe case
|
Death case
|
PE(+)
|
EV71(+)
|
Cox A16(+)
|
2016
|
19,512
|
237
|
2
|
98
|
168
|
24
|
2017
|
10242
|
75
|
2
|
95
|
29
|
54
|
2018
|
15977
|
150
|
0
|
124
|
0
|
3
|
2019
|
10090
|
6
|
0
|
40
|
2
|
34
|