The summary of DENV screening
We tested 2,254 donor samples for anti-DENV-IgG and anti-DENV-IgM antibodies by ELISA between June 2019 and October 2019 at Xishuangbanna Blood Center. Out of these samples, 598 were anti-DENV-IgG and/or IgM reactive by ELISA. Table 1 shows the demographic characteristics and DENV testing results of all donors in Xishuangbanna Blood Center.
Table 1. The Demographic Characteristics and serological prevalence of DENV in each group
Characteristics
|
Only
Anti-IgG reactive
|
Only
Anti-IgM reactive
|
Anti-IgG
And Anti-IgM reactive
|
Non-reactive
|
Total
|
Serological prevalence
(%)
|
χ2 and
P values
|
Donors Status
|
|
|
|
|
|
|
|
First-Time
|
267
|
28
|
31
|
809
|
1135(50.35%)
|
28.72
|
5.635, 0.018
|
Repeat
|
217
|
37
|
18
|
847
|
1119(49.65%)
|
24.30
|
|
Gender
|
|
|
|
|
|
|
|
Male
|
331
|
39
|
29
|
1033
|
1432(63.53%)
|
27.86
|
3.577, 0.059
|
Female
|
153
|
26
|
20
|
623
|
822 (%)
|
24.21
|
|
Age Group
|
|
|
|
|
|
|
|
18~25
|
84
|
10
|
6
|
294
|
394(17.48%)
|
25.38
|
9.337, 0.053
|
26~35
|
196
|
24
|
18
|
567
|
805(35.71%)
|
29.57
|
|
36~45
|
124
|
18
|
19
|
441
|
602(26.71%)
|
26.74
|
|
46~55
|
78
|
13
|
6
|
344
|
441(19.57%)
|
22.00
|
|
56~60
|
2
|
0
|
0
|
10
|
12(0.53%)
|
16.67
|
|
Occupation
|
|
|
|
|
|
|
|
Farmers
|
76
|
9
|
12
|
188
|
285(12.64%)
|
34.03
|
25.335, 0.001
|
Workers
|
34
|
3
|
3
|
116
|
156(6.92%)
|
25.64
|
|
Students
|
8
|
1
|
1
|
25
|
35(1.55%)
|
28.57
|
|
Soldiers
|
3
|
0
|
0
|
8
|
11(0.49%)
|
27.27
|
|
Teachers
|
4
|
0
|
0
|
34
|
38(1.69%)
|
10.53
|
|
Civil Servants
|
13
|
3
|
0
|
86
|
102(4.52%)
|
15.69
|
|
Medical staff
|
27
|
3
|
2
|
122
|
154(6.83%)
|
13.01
|
|
Employee
|
44
|
6
|
5
|
191
|
246(10.91%)
|
22.36
|
|
Others
|
275
|
40
|
26
|
886
|
1227(54.44%)
|
27.79
|
|
Education
|
|
|
|
|
|
|
|
BHS§
|
239
|
30
|
33
|
639
|
941(41.75%)
|
32.09
|
31.3, <0.001
|
HSAD*
|
66
|
9
|
4
|
210
|
289(12.82%)
|
27.33
|
|
Bachelor
|
43
|
8
|
1
|
227
|
279(12.38%)
|
18.64
|
|
Master
|
3
|
0
|
0
|
10
|
13(0.57%)
|
23.08
|
|
Others
|
133
|
18
|
11
|
570
|
732(32.48%)
|
22.13
|
|
Ethnicity
Han
Bai
Miao
Dai
Buliang
Hani
Other
|
240
2
6
73
14
70
79
|
35
1
0
7
1
11
10
|
27
0
0
8
1
3
10
|
885
17
12
188
18
248
288
|
1187(52.66%)
20(0.89%)
18(0.80%)
276(12.24%)
34(1.51%)
332(14.73%)
387(17.17%)
|
25.44
15.00
33.33
31.88
47.06
25.30
25.58
|
14.36, 0.026
|
Total
|
484
|
65
|
49
|
1656
|
2254
|
26.53
|
|
|
|
|
|
|
|
|
|
§BHS = Below High School
*HSAD = High School and Associate Degree
Serological prevalence of DENV
The total serological prevalence rate was 26.53%, and the serological prevalence were calculated in each group. The prevalence rate of the first-time and repeat donors were 28.72% and 24.30%, respectively. According to the Pearson's chi-square test, there was significant difference in the prevalence rate of DENV in first-time donors and repeat donors (P=0.018, χ2= 5.635). The prevalence rate was higher in male donors (27.86%) than female donors (24.21%), with 26~35 age group having the highest prevalence rate. In contrast, there was no significant difference in terms of gender (P=0.059, χ2= 3.577) and age group (P=0.053, χ2= 9.337). Further analysis revealed that there were significant differences in the prevalence rate of DENV in terms of occupation (P=0.001, χ2= 25.335), education(P<0.059, χ2= 31.30) and ethnicity (P=0.026, χ2= 14.358). In particular, the prevalence rate was the highest among farmer donors (34.03%), and there were significant differences in the prevalence rate of DENV between farmers and teachers (P=0.003, χ2= 8.622), civil servants (P<0.001, χ2= 12.233) and medical staff (P=0.004, χ2= 8.466). The prevalence rate in donors with below-high school (BHS), high school and associate (HSAD), bachelor, and master degrees, and others were 32.09%, 27.33%, 18.64%, 23.08%, 22.13%, respectively. There were significant difference in bachelor with BHS (P<0.001, χ2= 18.916) and HSAD (P<0.014, χ2= 6.052). The prevalence rate is the highest in Buliang nationality (47.06%), followed by Miao nationality (33.33%) and Dai nationality (31.88%); then by Han (25.44%), Bai (15.00%), Hani (25.30%) and other nationalities (25.58%). There were significant differences between Buliang and Bai (P=0.017, χ2=5.675), Hani (P=0.007, χ2= 7.353) and Han (P=0.005, χ2= 8.019). Table 1 displays the detailed information and serological prevalence rate of DENV in different groups.
DENV RNA testing by PCR and NS1 antigen testing by colloidal gold method
ELISA reactive samples
We detected 598 DENV reactive donor samples using ELISA. These samples were then tested for DENV RNA by PCR. Eight out of the 598 samples were tested positive. Then these 8 PCR positive samples and 142 PCR negative samples (choosing randomly from 590 PCR negative samples) were tested for NS1 antigen by colloidal gold method. Six out of the 8 samples were NS1 positive, whereas 2 out of the 142 samples were NS1 positive, with 6 out of the 142 samples being weakly positive (Their band is weaker than the control band).
ELISA non-reactive samples
We randomly chose 340 of the 1656 samples for RNA test by PCR, 5 were RNA positive. Then these 5 RNA positive samples were tested for NS1 antigen by colloidal gold method. Three out of 5 were NS1 positive. We then chose 50 of the 335 RNA negative samples to test NS1 antigen using colloidal gold method, 4 out of the 50 samples were weakly positive, only 1 out of 50 was positive.
Demographic characteristics of DENV positive donors
Table 2 showed the detailed information of donors who were both ELISA reactive and PCR and/or NS1 positive. There were 16 DENV screening reactive donor samples by ELISA, and these samples were PCR and/or NS1 positive. Of the 16 donors, 8 were females, the other 8 were males, with a range of age between 21 and 44 years old. Ten of 16 were first-time donors. Most of their education (11 out of 16) were high school and associate degree or below high school.
Table 2. The detailed information of donors who were ELISA reactive and PCR and/or NS1 Positive
Assigned Donor Number
|
Education
|
Occupation
|
Number of Blood Donation
|
Ethnicity
|
Blood Group
|
Results of Anti-IgG
|
Results
of
Anti-IgM
|
Results of NAT
|
Results of NS1
|
1
|
Bachelor
|
Medical staff
|
1
|
Dai
|
B
|
Reactive
|
Non-reactive
|
positive
|
Positive
|
2
|
High school
|
Others
|
2
|
Han
|
B
|
Reactive
|
Non-reactive
|
Positive
|
Positive
|
3
|
HSAD*
|
Employee
|
7
|
Dai
|
B
|
Reactive
|
Non-reactive
|
Positive
|
Positive
|
4
|
HSAD
|
Employee
|
1
|
Han
|
B
|
Reactive
|
Non-reactive
|
Positive
|
Positive
|
5
|
BHS§
|
Others
|
6
|
Han
|
B
|
Reactive
|
Non-reactive
|
Positive
|
Negative
|
6
|
BHS
|
Farmer
|
1
|
Dai
|
B
|
Reactive
|
Non-reactive
|
Positive
|
Positive
|
7
|
HSAD
|
Others
|
1
|
Dai
|
B
|
Reactive
|
Reactive
|
Positive
|
Positive
|
8
|
BHS
|
Others
|
1
|
Dai
|
O
|
Reactive
|
Reactive
|
Positive
|
Negative
|
9
|
HSAD
|
Others
|
1
|
Han
|
O
|
Reactive
|
Non-reactive
|
Negative
|
Positive
|
10
|
BHS
|
Others
|
2
|
Han
|
A
|
Reactive
|
Non-reactive
|
Negative
|
Positive
|
11
|
Bachelor
|
Employee
|
5
|
Han
|
O
|
Reactive
|
Non-reactive
|
Negative
|
WP▲
|
12
|
Bachelor
|
Employee
|
1
|
Lagu
|
A
|
Reactive
|
Non-reactive
|
Negative
|
WP
|
13
|
BHS
|
Others
|
5
|
Dai
|
A
|
Reactive
|
Non-reactive
|
Negative
|
WP
|
14
|
High school
|
Others
|
1
|
Yi
|
A
|
Reactive
|
Non-reactive
|
Negative
|
WP
|
15
|
BHS
|
Others
|
1
|
Hani
|
B
|
Reactive
|
Non-reactive
|
Negative
|
WP
|
16
|
BHS
|
Others
|
1
|
Han
|
A
|
Reactive
|
Non-reactive
|
Negative
|
WP
|
§BHS = Below High School
*HSAD = High School and Associate Degree
▲WP = Weakly Positive