Epidemiological characteristics of imported malaria in Zhejiang Province from 2020 to 2024

doi:10.12140/j.issn.1000-7423.2025.04.013

Abstract

Abstract:

Objective To investigate the epidemiological characteristics of imported malaria cases in Zhejiang Province, so as to provide insights into management of imported malari. Methods All data pertaining to malaria cases reported in Zhejiang Province from 2020 to 2024 were collected from China Disease Prevention and Control Information System and Parasitic Diseases Prevention and Control Information System, and malaria parasite species, temporal, spatial and population distributions, source of infections, time interval from illness onset to initial diagnosis, time interval from initial diagnosis to definite diagnosis, and relapse or recrudescence were descriptively analyzed among reported malaria cases. Chi-square test and nonparametric tests were used to compare differences. Results A total of 448 malaria cases were reported in Zhejiang Province from 2020 to 2024, with annual numbers of 53, 44, 64, 118 and 169 cases, respectively, and all cases were imported cases. Falciparum malaria was the predominant type, accounting for 77.23% (346/448), while ovale malaria, vivax malaria and malariae malaria accounted for 13.39% (60/448), 6.03% (27/448), and 3.35% (15/448), respectively. The reported malaria cases acquired infections across four continents, with Africa as the main source of infection (95.54%, 428/448) and there were 3 cases with cross-border mosquito-borne malaria. Malaria cases were reported across all 11 prefecturelevel cities in Zhejiang Province, with Hangzhou (29.24%, 131/448), Jinhua (25.67%, 115/448), and Wenzhou (10.49%, 47/448) reporting the highest number of cases. The number of reported malaria cases peaked in August in 2022 (15 cases) and remained elevated from July to October in both 2023 and 2024 (11-21 cases monthly). The reported cases included 412 males and 36 females, with a male-to-female ratio of 11.4 ∶ 1, and had a median age of 44 years. The accuracy of initial diagnosis was 75.89% (340/448) among reported malaria cases, and the median time intervals from illness onset to initial diagnosis and from initial diagnosis to definite diagnosis were both one day. 59.38% (266/448) of reported malaria cases sought healthcare within one day of illness onset, while 5.58% (25/448) sought treatment after more than 5 days. The proportion of falciparum malaria cases seeking healthcare within 2 days of onset (78.03%, 270/346) was higher than that of non-falciparum malaria cases (65.69%, 67/102) (χ² = 6.445, P < 0.05). There were 72.32% (324/448) of malaria cases receiving definite diagnosis within one day of initial diagnosis, while 4.91% (22/448) were diagnosed more than 5 days. The proportion of falciparum malaria cases diagnosed within 2 days (85.84%, 297/346) was higher than that of non-falciparum malaria cases (76.47%, 78/102) (χ² = 5.068, P < 0.05). In addition, total of 8 cases with malaria relapse or recrudescence were reported in Zhejiang Province, including 4 cases with falciparum malaria, 3 cases with ovale malaria and one case with vivax malaria. Conclusion The number of imported malaria cases appeared an upward trend in Zhejiang Province from 2020 to 2024. Intensified surveillance-response interventions and improved malaria diagnostic capability are recommended to prevent re-establishment of imported malaria.

Key words: Imported malaria, Epidemiological characteristic, Zhejiang Province

CLC Number:

R531.3

ZHANG Xuan, WANG Xiaoxiao, CHEN Hualiang, ZHANG Jiaqi, XU Wenjie, LU Qiaoyi, FENG Yan, RUAN Wei. Epidemiological characteristics of imported malaria in Zhejiang Province from 2020 to 2024[J]. CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES, 2025, 43(4): 533-539.

Figures/Tables 6

Table 1

Table 2

Table 3

Geographical distribution of imported malaria cases reported in Zhejiang Province from 2020 to 2024

地级市 Prefecture-level city	县（市、区）（病例数/例）Counties (City, District) （No. case)	合计例数 Total no. case
杭州 Hangzhou	上城区（15）、拱墅区（4）、西湖区（43）、滨江区（6）、萧山区（29）、余杭区（6）、临平区（6）、钱塘区（5）、富阳区（6）、临安区（2）、桐庐县（5）、淳安县（2）、建德市（2）Shangcheng (15), Gongshu (4), Xihu (43), Binjiang (6), Xiaoshan (29), Yuhang(6), Linping (6), Qiantang (5), Fuyang (6), Lin’an (2), Tonglu (5), Chun'an (2), Jiande(2)	131
宁波 Ningbo	海曙区（9）、镇海区（2）、鄞州区（8）、余姚市（3）、慈溪市（2）、象山县（3）Haishu (9), Zhenhai (2), Yinzhou (8), Yuyao (3), Cixi (2), Xiangshan (3)	27
温州 Wenzhou	鹿城区（16）、龙湾区（1）、瓯海区（12）、乐清市（5）、瑞安市（7）、文成县（2）、苍南县（4） Lucheng (16), Longwan (1), Ouhai (12), Yueqing (5), Rui’an (7), Wencheng (2), Cangnan (4)	47
湖州 Huzhou	吴兴区（9）、长兴县（3）Wuxing (9), Changxing (3)	12
嘉兴 Jiaxing	南湖区（7）、嘉善县（2）、海宁市（1）、桐乡市（2）Nanhu (7), Jiashan (2), Haining (1), Tongxiang (2)	12
绍兴 Shaoxing	越城区（6）、柯桥区（10）、上虞区（4）、诸暨市（11）、嵊州市（2）、新昌县（1）Yuecheng (6), Keqiao (10), Shangyu (4), Zhuji (11), Shengzhou (2), Xinchang (1)	34
金华 Jinhua	婺城区（4）、金东区（2）、兰溪市（2）、东阳市（10）、义乌市（89）、永康市（4）、浦江县（1）、武义县（2）、磐安县（1）Wucheng (4), Jindong (2), Lanxi (2), Dongyang (10), Yiwu (89), Yongkang (4), Pujiang (1), Wuyi (2), Pan’an (1)	115
衢州 Quzhou	柯城区（1）、衢江区（2）、龙游县（3）、江山市（3）Kecheng (1), Qujiang (2), Longyou (3), Jiangshan (3)	9
舟山 Zhoushan	定海区（4）、普陀区（2）Dinghai (4), Putuo (2)	6
台州 Taizhou	椒江区（6）、黄岩区（1）、路桥区（5）、临海市（1）、温岭市（18）、玉环市（3）、天台县（4）Jiaojiang (6), Huangyan (1), Luqiao (5), Linhai (1), Wenling (18), Yuhuan (3), Tiantai (4)	38
丽水 Lishui	莲都区（11）、龙泉市（3）、青田县（3）Liandu (11), Longquan (3), Qingtian (3)	17

Table 3

Fig. 1

Table 4

Table 5

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疟疾类型Malaria type	病例例数（占比/%） No. cases (Proportion/%)
疟疾类型Malaria type	2020	2021	2022	2023	2024	合计 Total
恶性疟Falciparum malaria	29(54.72)	29(65.91)	50(78.13)	105(88.98)	133(78.70)	346(77.23)
间日疟Vivax malaria	4(7.55)	0(0)	3(4.69)	6(5.08)	14(8.28)	27(6.03)
卵形疟Ovale malaria	18(33.96)	11(25.00)	7(10.94)	6(5.08)	18(10.65)	60(13.39)
三日疟Malariae malaria	2(3.77)	4(9.09)	4(6.25)	1(0.85)	4(2.37)	15(3.35)
合计Total	53(100)	44(100)	64(100)	118(100)	169(100)	448(100)

感染来源 Infection source	恶性疟 Falciparum malaria	间日疟 Vivax malaria	卵形疟 Ovale malaria	三日疟 Malariae malaria	合计 Total
非洲 Africa
尼日利亚 Nigeria	83	0	17	2	102
喀麦隆 Cameroon	35	0	15	5	55
刚果（金）Democratic Republic of the Congo	26	4	6	1	37
几内亚 Guinea	31	0	1	2	34
加纳 Ghana	30	0	1	0	31
科特迪瓦 Cote d’lvoire	19	0	4	1	24
安哥拉 Angola	14	0	1	2	17
乌干达 Uganda	11	2	2	1	16
塞拉利昂 Sierra Leone	11	0	2	0	13
乍得 Chad	11	0	0	0	11
加蓬 Gabon	5	0	4	1	10
坦桑尼亚 Tanzania	6	0	2	0	8
南苏丹 South Sudan	6	0	1	0	7
赤道几内亚 Equatorial Guinea	6	0	1	0	7
马里 Mali	6	0	1	0	7
刚果（布）Republic of the Congo	6	0	0	0	6
赞比亚 Zambia	5	0	1	0	6
中非 Central African Republic	3	0	1	0	4
埃塞俄比亚 Ethiopia	1	3	0	0	4
塞内加尔 Senegal	4	0	0	0	4
苏丹 Sudan	3	0	0	0	3
卢旺达 Rwanda	3	0	0	0	3
尼日尔 Niger	3	0	0	0	3
科摩罗 Comoros	3	0	0	0	3
其余9国家 9 other countries	12	1	0	0	13
亚洲 Asia
巴基斯坦 Pakistan	1	6	0	0	7
阿富汗 Afghanistan	0	1	0	0	1
泰国 Thailand	1	0	0	0	1
缅甸 Myanmar	0	1	0	0	1
印度 India	0	1	0	0	1
印度尼西亚 Indonesia	0	1	0	0	1
跨境蚊传 Cross-border mosquito-borne malaria	0	3	0	0	3
大洋洲 Oceania
巴布亚新几内亚 Papua New Guinea	1	3	0	0	4
中美洲 Central America
尼加拉瓜 Nicaragua	0	1	0	0	1
合计 Total	346	27	60	15	448

分类 Variable	发病到初诊时间间隔/d Time interval from illness onset to initial care-seeking/d		初诊到确诊时间间隔/d Time interval from initial care-seeking to diagnosis/d
分类 Variable	中位数（四分位数）Median (IRQ)	P值 P value	中位数（四分位数）Median (IRQ)	P值 P value
年份 Year		< 0.01		> 0.05
2020	1(0,3)		1(0,2)
2021	0(0,1)		1(1,2)
2022	1(0,2.5)		1(0,1)
2023	1(0,2)		1(0,2)
2024	2(0,3)		1(0,2)
疟疾类型 Malaria type		< 0.05		< 0.05
恶性疟 Falciparum malaria	1(0,2)		1(0,2)
间日疟 Vivax malaria	2(0,4)		1(0,3)
卵形疟 Ovale malaria	2(0,3)		1(0,2)
三日疟 Malariae malaria	1(0,5)		1(1,3)

年份 Year	病例数 No. case	疟疾类型 Malaria type	感染地区 Infection area
2022	2	恶性疟（1例），卵形疟（1例） Falciparum malaria (1 case), Ovale malaria (1 case)	加纳，喀麦隆 Ghana, Cameroon
2023	3	恶性疟（1例），卵形疟（2例） Falciparum malaria (1 case), Ovale malaria (2 cases)	几内亚，尼日利亚，加蓬 Guinea, Nigeria, Gabon
2024	3	恶性疟（2例），间日疟（1例） Falciparum malaria (2 cases), Vivax malaria (1 case)	加纳，乌干达，巴布亚新几内亚 Ghana, Uganda, Papua New Guinea