History of malaria surveillance in Sanya and in Hainan
Hainan had malaria endemic areas of P. falciparum and P. vivax. Since 1954, a parasite survey of local residents (PSLR), which acted as a type of surveillance for ACD, was conducted in Hainan Province every year. From PSLR recordings, 10 cases (CI: 2-42) of P. malariae were found every year in Hainan Province before 1964. However, Sanya also conducted PSLR but found only P. falciparum malaria and P. vivax since 1959[16]. From IDIRMS, 27 malaria cases were reported in Sanya from 2009 to 2018, including 6 cases of P. falciparum malaria, 10 cases of P. vivax malaria, 6 cases of P. malariae malaria, 1 case of P. ovale malaria, and 4 cases of unclassified malaria. During the malaria elimination phase from 2011 to 2018, a total of 14 cases of malaria were reported in Sanya city, including 8 indigenous cases and 6 imported cases. The indigenous cases reported in 2011 were P. vivax. No cases were reported from 2012 to 2014 and 2017[17]. In 2015, 6 indigenous cases of P. malariae were found (Fig. 1).
Established epidemic response for forest-goers in TLS in 2015
Three villages in Gaofeng town of Sanya city were selected as the first layer, including Baolong, Lixin and Zhanan. Seven villages in Xinzheng Town, Baoting County, were also selected as the first layer, including shirang, maowen, xinzheng, maopeng, baodao, shenna and nangai; All of the residents were targeted except for migrants and were not suitable for users, with active case detection (ACD). 1,823 blood slides and PCR screening from villages in Baoting and Sanya were conducted on all residents. Three positive samples were found from blood samples, and thirteen positive samples were found from PCR. After cross-checking, four cases were identified and other false positives were ruled out, including Case 2, 3, 4 and Case 6. Case 5 was found when he went to the hospital voluntarily. they were confirmed to be infected with P. malariae. In the second layers, ten townships were chosen, and passive case detection (PCD) and active case detection (ACD) for forest-goers were conducted mainly in Gaofeng townships of the foci and surrounding townships, including Gaofeng, Yucai in Sanya city, Daan, Zhizhong in Ledong County, Xiangshui, Maogan, Nanlin, Sandao, Xinzhen in Baoting County and Changhao in Wuzhishan City. 7,831 blood slides were screened from target townships and tests conducted on all forest-goers. In the third layer, 12 counties or cities were selected for health education, and passive case detection was conducted mainly around Sanya and the associated counties for forest-goers, including Ledong, Baoting, Wuzhishan, Dongfang, Lingshui, Qiongzhong, Baisha, Changjiang, Wanning, Qionghai, Tunchang and Danzhou. 95,350 blood slides were screened from target townships, and tests were conducted on all forest-goers (Table 1). Meanwhile, vector surveillance and control were also conducted to support foci disposals and to minimize the possibility of transmission (Table 2).
Table 1
Three-layer strategy conducted in epidemic response in 2015 and intervention from 2016 to 2018
Layers
|
Names of counties or cities
|
Names of township
|
Names of village
|
Three-layer strategy (TLS)
|
Epidemic response in 2015
|
Strengthened intervention from 2016 to 2018
|
PCD
|
ACD
|
2016
|
2017
|
2018
|
ACD in
|
CP
|
%
|
Ne.
|
Pos.
|
Ne.
|
Pos.
|
MPD
|
MPD
|
MPD
|
FG
|
|
|
1st Layer
|
Sanya
|
Gaofeng
|
Baolong†
|
67
|
0
|
400
|
0
|
50
|
51
|
29
|
256
|
216
|
84.4%
|
Lixin†
|
74
|
0
|
558
|
4
|
55
|
46
|
34
|
827
|
663
|
80.2%
|
Zhanan†
|
35
|
1
|
684
|
0
|
29
|
46
|
58
|
1030
|
946
|
91.8%
|
Baoting
|
xinzheng
|
shirang
|
58
|
0
|
17
|
0
|
107
|
150
|
3
|
116
|
116
|
100.0%
|
maowen
|
45
|
0
|
5
|
0
|
37
|
17
|
0
|
173
|
171
|
98.8%
|
xinzheng
|
39
|
0
|
8
|
0
|
288
|
14
|
0
|
275
|
250
|
90.9%
|
maopeng
|
53
|
0
|
7
|
0
|
50
|
29
|
1
|
103
|
96
|
93.2%
|
baodao
|
43
|
0
|
11
|
0
|
39
|
16
|
0
|
57
|
54
|
94.7%
|
shenna
|
41
|
0
|
27
|
0
|
35
|
11
|
0
|
116
|
116
|
100.0%
|
nangai
|
41
|
0
|
106
|
0
|
137
|
184
|
0
|
173
|
171
|
98.8%
|
2nd Layer
|
Sanya
|
Gaofeng*
|
1216
|
0
|
0
|
0
|
1071
|
178
|
165
|
0
|
0
|
0
|
Yucai
|
1109
|
0
|
553
|
0
|
602
|
1109
|
1219
|
1297
|
1265
|
97.5%
|
ledong
|
Daan
|
83
|
0
|
317
|
0
|
550
|
550
|
548
|
5
|
5
|
100.0%
|
Zhizhong
|
548
|
0
|
32
|
0
|
702
|
714
|
664
|
378
|
375
|
99.2%
|
Baoguo
|
82
|
0
|
447
|
0
|
513
|
552
|
520
|
30
|
24
|
80.0%
|
Baoting
|
Xiangshui
|
331
|
0
|
103
|
0
|
475
|
474
|
471
|
415
|
375
|
90.4%
|
Maogan
|
350
|
0
|
0
|
0
|
549
|
414
|
588
|
1381
|
341
|
24.7%
|
Nanlin
|
600
|
0
|
258
|
0
|
747
|
686
|
610
|
478
|
478
|
100.0%
|
Xinzheng
|
742
|
0
|
0
|
0
|
797
|
557
|
425
|
707
|
707
|
100.0%
|
Sandao
|
740
|
0
|
0
|
0
|
708
|
554
|
481
|
427
|
414
|
97.0%
|
Wuzhishan
|
changhao
|
320
|
0
|
0
|
0
|
317
|
444
|
302
|
371
|
360
|
97.0%
|
3rd Layer
|
Sanya*
|
11039
|
0
|
15
|
0
|
10815
|
8183
|
9186
|
0
|
0
|
0
|
Ledong
|
4261
|
0
|
4332
|
0
|
8372
|
8533
|
8662
|
191
|
178
|
93.2%
|
Baoting*
|
5529
|
0
|
142
|
0
|
7371
|
4878
|
5330
|
0
|
0
|
0
|
Wuzhishan
|
2120
|
0
|
885
|
0
|
2972
|
3009
|
2472
|
726
|
712
|
98.1%
|
Dongfang
|
9496
|
0
|
0
|
0
|
9308
|
9755
|
9462
|
489
|
473
|
96.7%
|
Lingshui
|
5359
|
0
|
1747
|
0
|
7421
|
7171
|
7477
|
833
|
808
|
97.0%
|
Qiongzhong
|
3427
|
0
|
2640
|
0
|
5965
|
6724
|
5975
|
427
|
425
|
99.5%
|
Baisha
|
6828
|
0
|
588
|
0
|
7365
|
7342
|
6354
|
207
|
207
|
100.0%
|
Changjiang
|
2294
|
0
|
2923
|
0
|
5226
|
5172
|
5334
|
1418
|
1417
|
99.9%
|
Waning
|
9354
|
0
|
1115
|
0
|
13616
|
11287
|
18427
|
3732
|
3366
|
90.2%
|
Qionghai
|
5582
|
0
|
1624
|
0
|
8030
|
7604
|
6742
|
2016
|
1952
|
96.8%
|
Tunchang
|
1969
|
0
|
1626
|
0
|
3523
|
3598
|
3098
|
0
|
0
|
0
|
Danzhou
|
10297
|
0
|
158
|
0
|
9602
|
93687
|
9111
|
325
|
319
|
98.2%
|
Total
|
|
84172
|
1
|
21328
|
4
|
107044
|
183739
|
103748
|
18979
|
17000
|
89.6%
|
†Baolong village consists 4 units, Hongqi, Zhatao, Zhaban, Xianjin; Zhanan village consists of 8 units, Nanjin, Hongxing, Jiayue, xincun, Baotu, Ganyou, Lingqu; Lixin village consists of 4 units, Zhayun, Zhaka, Zhaye, Zhachu, Zhaye ,xincun; |
* The data has been shown in the previous layer. |
MPD: malaria parasite detection;FG:Forest goer;CP: chemoprevention;ACD: active case detection; PCD:passive case detection |
Table 2
Vector Surveillance and control from 2015 to 2018
Names of counties or cities
|
Vector Surveillance
|
Vector Control*
|
2015
|
2016
|
2017
|
2018
|
Distribution LLNts
|
An.
minus
|
An.
dirus
|
An. sinensis
|
others
|
An.
minus
|
An.
dirus
|
An.
sinensis
|
others
|
An.
minus
|
An.
dirus
|
An. sinensis
|
others
|
An.
minus
|
An.
dirus
|
An. sinensis
|
others
|
2015
|
2016
|
2017
|
2018
|
Sanya
|
1
|
0
|
154
|
2337
|
1
|
2
|
368
|
50
|
0
|
0
|
548
|
140
|
0
|
0
|
187
|
136
|
300
|
1648
|
598
|
490
|
Ledong
|
0
|
0
|
164
|
283
|
0
|
0
|
182
|
143
|
0
|
0
|
105
|
60
|
0
|
0
|
83
|
30
|
447
|
325
|
165
|
113
|
Baoting
|
0
|
0
|
0
|
15
|
0
|
0
|
319
|
204
|
0
|
0
|
131
|
352
|
0
|
0
|
9
|
15
|
600
|
1700
|
0
|
0
|
Wuzhishan
|
2
|
18
|
74
|
29
|
2
|
19
|
49
|
5
|
0
|
34
|
10
|
2
|
2
|
21
|
21
|
7
|
600
|
1000
|
0
|
0
|
Dongfang
|
0
|
0
|
92
|
296
|
0
|
0
|
11
|
85
|
0
|
0
|
181
|
423
|
0
|
0
|
207
|
1178
|
700
|
500
|
0
|
0
|
Lingshui
|
0
|
0
|
95
|
273
|
0
|
0
|
241
|
802
|
0
|
0
|
236
|
675
|
0
|
0
|
88
|
420
|
409
|
670
|
0
|
495
|
Qiongzhong
|
0
|
0
|
357
|
226
|
0
|
0
|
119
|
17
|
0
|
0
|
61
|
16
|
0
|
0
|
36
|
2
|
600
|
700
|
0
|
0
|
Baisha
|
3
|
19
|
910
|
1126
|
9
|
0
|
242
|
409
|
0
|
0
|
418
|
126
|
1
|
0
|
224
|
48
|
600
|
700
|
0
|
0
|
Changjiang
|
100
|
0
|
327
|
1137
|
0
|
40
|
116
|
268
|
1
|
3
|
93
|
212
|
1
|
0
|
9
|
124
|
1564
|
424
|
309
|
134
|
Wanning
|
0
|
0
|
97
|
214
|
0
|
0
|
116
|
164
|
0
|
0
|
94
|
154
|
0
|
0
|
65
|
146
|
0
|
0
|
0
|
0
|
Qionghai
|
0
|
0
|
0
|
0
|
1
|
0
|
663
|
185
|
1
|
0
|
107
|
312
|
23
|
0
|
53
|
261
|
2610
|
2409
|
1415
|
0
|
Tunchang
|
17
|
0
|
1249
|
2927
|
9
|
0
|
1081
|
3647
|
19
|
0
|
2253
|
3110
|
0
|
0
|
470
|
177
|
0
|
300
|
0
|
0
|
Danzhou
|
154
|
0
|
73
|
11
|
37
|
0
|
124
|
154
|
1
|
0
|
108
|
10
|
0
|
0
|
120
|
0
|
300
|
300
|
0
|
60
|
Total
|
277
|
37
|
3592
|
8874
|
59
|
61
|
3631
|
6133
|
22
|
37
|
4345
|
5592
|
27
|
21
|
1572
|
2544
|
8730
|
10676
|
2487
|
1292
|
*The data of IRS didn’t showed and IRS implemented only in Sanya for disposal six focis. |
Strengthened intervention on forest-goers in TLS from 2016 to 2018
Target villages between 2016 and 2018 were included in the epidemic response strategy for forest-goers in 2015, but residents adopted the number of residents at that time. Piperaquine phosphate was selected as a chemoprophylactic drug. In March from 2016 to 2018, residents in the targeted villages were given a total dose of 1200 mg orally before bedtime for adults within 3 days, from 2016 to 2018. Starting in April from 2016 to 2018, forest-goers were administered 600 mg orally for adults before bedtime within a day. Doses for children decreased by weight or age. Villagers, including forest-goers, were required to sign informed consent before administration. At the same time, active case detection (ACD) should be conducted while seeking forest-goers. If fever is found in forest-goers, examination for malaria must be performed, including microscopy.(Fig. 2)
In the first layer, chemoprophylaxis and ACD were conducted on residents in the villages of the foci and the surrounding villages, and 89.5% residents accepted chemoprophylaxis. In the second layer, chemoprophylaxis and ACD while seeking forest-goers were conducted mainly in the townships of the foci and the surrounding townships. Of the 5,489 people who were forest-goers, 79.1% received chemoprophylaxis while seeking forest-goers. In the third layer, preventive medication and health education were conducted in Sanya and the associated counties for forest-goers. Of the 10,364 people who belonged to forest-goers, 89.6% received chemoprophylaxis while seeking forest-goers. Meanwhile, the training of clinicians, public health and laboratory personnel was strengthened to improve the capacity to respond to the epidemic from 2015 to 2018 (Table 3).
Table 3
Training in 13 counties or cities for response and intervention from 2015 to 2018
Names of counties or cities
|
Clinician
|
Public Health Doctor
|
Laboratory Technicians
|
2015
|
2016
|
2017
|
2018
|
2015
|
2016
|
2017
|
2018
|
2015
|
2016
|
2017
|
2018
|
Sanya
|
23
|
18
|
20
|
24
|
36
|
24
|
20
|
22
|
29
|
18
|
26
|
19
|
Ledong
|
25
|
26
|
46
|
0
|
51
|
68
|
34
|
23
|
25
|
26
|
46
|
23
|
Baoting
|
28
|
23
|
24
|
17
|
83
|
43
|
72
|
20
|
16
|
17
|
19
|
15
|
Wuzhishan
|
9
|
11
|
10
|
0
|
10
|
10
|
10
|
23
|
10
|
10
|
6
|
0
|
Dongfang
|
24
|
21
|
22
|
27
|
42
|
42
|
22
|
27
|
23
|
21
|
23
|
22
|
Lingshui
|
21
|
46
|
56
|
22
|
45
|
66
|
56
|
56
|
42
|
25
|
22
|
22
|
Qiongzhong
|
105
|
0
|
25
|
24
|
0
|
0
|
0
|
0
|
2
|
0
|
27
|
4
|
Baisha
|
26
|
85
|
24
|
0
|
42
|
54
|
0
|
0
|
31
|
38
|
26
|
0
|
Changjiang
|
10
|
16
|
27
|
0
|
21
|
21
|
30
|
33
|
14
|
25
|
30
|
25
|
Waning
|
15
|
100
|
24
|
23
|
335
|
190
|
24
|
24
|
0
|
32
|
22
|
20
|
Qionghai
|
10
|
0
|
73
|
27
|
70
|
60
|
51
|
21
|
34
|
0
|
20
|
17
|
Tunchang
|
25
|
11
|
19
|
44
|
21
|
20
|
15
|
45
|
18
|
14
|
22
|
38
|
Danzhou
|
28
|
18
|
17
|
0
|
106
|
34
|
17
|
23
|
47
|
32
|
17
|
0
|
Total
|
349
|
375
|
387
|
208
|
862
|
632
|
351
|
317
|
291
|
258
|
306
|
205
|
Case reports and epidemiological characteristics of this outbreak under TLS guideline
A total of 6 P. malariae cases occurred in Sanya city in 2015 under TLS guideline. All cases except for the index case (case 1) were reported within 1 day through IDIRMS. From PDIRMS, None of the 6 patients had a history of travelling abroad, previous malaria or blood transfusion. Six cases were regarded as indigenous cases of P. malariae. All of the reported cases were confirmed by microscopy and sequencing. These cases were reported between September and November: 3 cases in September, 1 case in October and 1 case in November. The age group (19-40 years of age) belonged to the younger-middle age group. They were all males and farmers in occupational categories. The total indigenous cases were reported at the Gaofeng township level (N=6, 100%) or in 3 villages. Two cases(Case 1 and 5) were found by passive case detection (PCD), but 4 cases were found by active case detection (ACD) in their villages (Table 4). We also collected information about the outpatient visiting behaviors and found that 100% of patients visited local village clinics after experiencing fever symptoms. However, only 16% (case 1) of patients were diagnosed with malaria in county-level hospitals, although 33% (cases 1 and 5) continued to higher-level hospitals, including township-level or/and county-level hospitals.
Table 4
Demographic epidemic characteristics of cases
|
No. Cases (N=6)
|
(%)
|
Ages
|
|
|
<20
|
1
|
16.7%
|
20-30
|
2
|
33.3%
|
30-40
|
3
|
50%
|
Gender
|
|
|
male
|
6
|
100%
|
Address
|
|
|
Gaofeng towns
|
6
|
100%
|
Village
|
|
|
Baolong
|
1
|
16.7%
|
Lixin
|
4
|
66.7%
|
Zhanan
|
1
|
16.7%
|
Number of forest goer
|
5
|
83.3%
|
Source of cases
|
|
|
PCD
|
2
|
33.3%
|
ACD
|
4
|
66.7%
|
1-3-7 implement
|
|
|
Report within 24h
|
5
|
83.3%
|
Confirmation and epidemical investigation within 3 days
|
6
|
100%
|
Foci classification and response within 7 days
|
6
|
100%
|
From the results of the epidemic survey, 5 patients had a history of night sleeping in mountains before the onset of fever and were classified as forest-goers. However, one case (case 6) had no above mentioned history before the onset of fever. A total of 5 cases (Case1, Case2, Case3, Case4, Case5) had a history of collecting bodhi fruit (Daemonoropus margaritae Becc varpalawanica) or honey in the mountains in almost all months of the year. Case 1, who coworked with cases 2, 3 and 4, climbed mountains and slept overnight to collect bodhi fruit, and case 5, who coworked with the other 2 persons, did so also. However, Case 6 stayed in villages and had no history of staying in mountains overnight. From Case 1 to Case 5, infection with P. malariae was associated with the behaviour of overnights in the mountains. Moreover, infection also occurred in the village from case 6 (Fig. 3).
Infection source
A total of 6 cases were found in this epidemic, among which 5 cases belonged to forest-goers, who had a history of overnight sleeping in the mountains, and 1 case did not belong to forest-goers and had no history of overnight sleeping in mountains. At present, there are three possible sources of infection in mosquito-borne malaria cases: 1) transmission caused by a long incubation period. 2) transmission caused by imported sources of infection and subsequent reintroduction. 3) transmission from an animal host in forests. Based on the epidemic characteristics of these cases, especially age characteristics, the second is more likely, the third is possible, and the first is almost impossible.