Epidemiological characteristics and influencing factors of severe cases of imported malaria in Shandong Province from 2015 to 2025

doi:10.12140/j.issn.1000-7423.2026.04.015

Abstract

Abstract:

Objective To investigate the epidemiological characteristics and influencing factors of imported severe malaria cases in Shandong Province from 2015 to 2025, so as to provide insights into formulation of control strategies targeting the reduction of severe malaria cases. Methods The epidemic status of imported malaria and epidemiological case surveys of malaria cases in Shandong Province from 2015 to 2025 were collected from the Notifiable Disease Report Information Management System and Parasitic Diseases Prevention and Control Information Management System of China Information System for Disease Control and Prevention. The species of malaria parasites, source of acquiring infections, temporal, spatial and population distributions, healthcare seeking behaviors and definitive diagnosis of severe malaria cases were analyzed using a descriptive epidemiological method, and factors affecting the development of severe cases were identified with a logistic regression model. Results A total of 2 004 malaria cases were reported in Shandong Province from 2015 to 2025, including 155 severe cases (7.73%). Among the severe cases, there were 138 cases with falciparum malaria (89.03%), 10 cases with vivax malaria (6.45%), 6 cases with ovale malaria (3.87%), and 1 case with malariae malaria (0.65%), with 96.77% imported from African countries and 3.23% from Asian countries. Severe malaria cases were reported across all cities in Shandong Province except Heze City, with Qingdao City (46 cases, 29.68%), Jinan City (37 cases, 23.87%), and Jining City (16 cases, 10.32%) as the three most highly affected cities. There were 48 severe malaria cases (30.97%) receiving trans-regional medical services within the province. Of severe malaria cases, there were 149 males (96.13%) and 6 females (3.87%), with an average age of 41 years, and labors as the predominant occupation (69.68%, 108/155). The highest number of severe malaria cases was recorded in January (21 cases, 10.34% of monthly cases), while the lowest number was reported in March and April (8 cases each, 5.16% of monthly cases). The median interval from disease onset to initial diagnosis was 2 days among severe malaria cases, and the median interval from initial diagnosis to definitive diagnosis was 1 day. There were 13 cases (8.39%), 62 cases (40.00%), 42 cases (27.10%), 28 cases (18.06%), and 10 cases (6.45) receiving initial diagnoses at provincial, municipal, county, sub-county, and other institutions (disease control and prevention institutions and private doctors), with correct first-diagnosis rates of 12/13, 75.81% (47/62), 45.24% (19/42), 3.57% (1/28), and 3/10, respectively. Multivariate logistic regression analysis identified age group of 50-59 years (OR = 2.076, 95% CI : 1.081 to 3.986), occupation of housework or unemployed (OR = 1.989, 95% CI: 1.134 to 3.490), disease onset out of China (OR = 2.139, 95% CI: 1.287 to 3.555), history of malaria (OR = 0.364, 95% CI: 0.254 to 0.521), interval from initial diagnosis to definitive diagnosis of 3 days and longer (OR = 2.120, 95% CI: 1.252 to 3.591), falciparum malaria (OR = 2.798, 95% CI: 1.633 to 4.792), and cross-regional healthcare-seeking behaviors (OR = 1.741, 95% CI: 1.185 to 2.558) as factors affecting the development of severe malaria. Conclusion The proportion of imported severe malaria cases is high in Shandong Province. Old age, long duration from initial diagnosis to definitive diagnosis, P. falciparum infection, and cross-regional healthcare-seeking behaviors increase the risk of severe malaria.

Key words: Severe case, Imported malaria, Epidemiological characteristic, Risk factor

CLC Number:

R531.32

MA Yufang, XU Yan, WANG Yongbin, WANG Longjiang, LI Yuejin, BU Cancan, LV Wenxiang, LI Yuanchang, XU He, ZHANG Shengnan, KONG Xiangli. Epidemiological characteristics and influencing factors of severe cases of imported malaria in Shandong Province from 2015 to 2025[J]. CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES, 2026, 44(4): 557-564.

Figures/Tables 5

Fig. 1

Table 1

Table 2

Table 3

Univariate analysis of imported severe and non-severe malaria in Shandong Province from 2015 to 2025

因素 Variable	总计 Total		重症病例 Severe cases		非重症病例 Non-severe cases		χ²值 χ² value	P值 P value
因素 Variable	病例 No. case	构成比/% Proportion/%	病例数No. case	构成比/% Proportion/%	病例数No. case	构成比/% Proportion/%	χ²值 χ² value	P值 P value
年龄 Age							4.372	0.037
< 30	246	12.28	15	9.68	231	12.49
30~39	577	28.79	37	23.87	540	29.20
40~49	733	36.58	60	38.71	673	36.40
50~59	406	20.26	39	25.16	367	19.85
≥ 60	42	2.10	4	2.58	38	2.06
性别 Sex							4.762	0.029
男 Male	1 970	98.30	149	96.13	1 821	98.49
女 Female	34	1.70	6	3.87	28	1.51
国籍 Nationality							0.641	0.423
中国籍 Chinese	1 960	97.80	153	98.71	1 807	97.73
外国籍 Foreign	44	2.20	2	1.29	42	2.27
职业 Occupation							9.665	0.046
务工 Migrant worker	1 565	78.09	108	69.68	1 457	78.80
商业服务 Commercial service workers	53	2.64	4	2.58	49	2.65
家务及待业 Housework & unemployed	136	6.79	18	11.61	118	6.38
干部职员 Cadres and office staff	124	6.19	14	9.03	110	5.95
其他 Others	126	6.29	11	7.10	115	6.22
发病地点 Place of onset							13.380	0.000
国内 Domestic	1 855	92.56	132	85.16	1 723	93.19
国外 Foreign	149	7.44	23	14.84	126	6.81
疟疾史 History of malaria							59.155	0.000
有 Yes	1 282	63.97	55	35.48	1 227	66.36
无 No	722	36.03	100	64.52	622	33.64
初诊机构属性 Nature of initial diagnosis institution							4.579	0.333
省级 Provincial level	221	11.03	13	8.39	208	11.25
市级 Municipal level	715	35.68	62	40.00	653	35.32
县级 County level	689	34.38	46	29.68	643	34.78
县级以下 Below county level	291	14.52	28	18.06	263	14.22
其他 Others	88	4.39	6	3.87	82	4.43
初诊结果 Initial diagnosis							18.430	0.000
疟疾 Malaria	1 369	68.31	82	52.90	1 287	69.61
其他疾病 Other diseases	635	31.69	73	47.10	562	30.39
发病到初诊时间间隔 Onset to initial diagnosis							1.849	0.174
0 d	600	29.94	45	29.03	555	30.02
1~3 d	991	49.45	68	43.87	923	49.92
> 3 d	413	20.61	42	27.10	371	20.06
初诊到确诊时间间隔 Initial diagnosis to confirmation							25.116	0.000
0 d	988	49.30	52	33.55	936	50.62
1~3 d	709	35.38	60	38.71	649	35.10
> 3 d	307	15.32	43	27.74	264	14.28
疾病类型 Type of disease							20.261	0.000
恶性疟 Falciparum malaria	1 478	73.75	138	89.03	1 340	72.47
非恶性疟 Non-falciparum malaria	526	26.25	17	10.97	509	27.53
跨地区就诊 Cross-regional medical treatment							15.595	0.000
是 Yes	381	19.01	48	31.00	333	18.00
否 No	1 623	80.99	107	69.00	1 516	82.00

Table 3

Table 4

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市 City	按报告地统计 Statistics according to the report city		按现住地统计 Statistics according to the present address
市 City	病例数/例 No. case	跨地区就诊病例数（占比/%）No. case with cross-regional medical visits (proportion/%)	病例数/例No. case	跨地区就诊病例数（占比/%）No. case with cross-regional medical visits (proportion/%)
济南 Jinan	37	29（78.38）	9	1（1/9）
青岛 Qingdao	46	9（19.57）	37	0（0）
淄博 Zibo	4	0（0）	5	1（1/5）
枣庄 Zaozhuang	1	0（0）	2	1（1/2）
东营 Dongying	4	0（0）	6	2（2/6）
烟台 Yantai	8	0（0）	10	2（2/10）
潍坊 Weifang	2	0（0）	7	5（5/7）
济宁 Jining	16	5（5/16）	12	1（1/12）
泰安 Taian	4	0（0）	13	9（9/13）
威海 Weihai	10	1（1/10）	10	1（1/10）
日照 Rizhao	4	0（0）	7	3（3/7）
临沂 Linyi	16	2（2/16）	18	4（4/18）
德州 Dezhou	1	1（1/1）	6	6（6/6）
聊城 Liaocheng	1	0（0）	2	1（1/2）
滨州 Binzhou	1	1（1/1）	0	0（0）
菏泽 Heze	0	0（0）	9	9（9/9）
合计 Total	155	48（30.97）	153	46（30.07）

因素 Variable	分类 Classification	β	SE	Waldχ²	P	OR	95% CI
年龄 Age	< 30					1
	30~39	0.286	0.332	0.742	0.389	1.331	0.695~2.550
	40~49	0.487	0.315	2.384	0.123	1.627	0.877~3.017
	50~59	0.730	0.333	4.814	0.028	2.076	1.081~3.986
	≥ 60	0.515	0.615	0.701	0.402	1.674	0.501~5.594
性别 Sex	男Male					1
性别 Sex	女 Female	0.801	0.499	2.581	0.108	2.228	0.838~5.919
职业	务工 Migrant worker					1
Occupation	商业服务 Commercial service workers	0.113	0.546	0.043	0.835	1.120	0.384~3.266
	家务及待业 Housework & unemployed	0.688	0.287	5.748	0.017	1.989	1.134~3.490
	干部职员 Cadres and office staff	0.389	0.316	1.513	0.219	1.476	0.794~2.744
	其他 Others	0.213	0.349	0.373	0.541	1.237	0.625~2.451
发病地点	国内 Domestic					1
Place of onset	国外 Foreign	0.760	0.259	8.594	0.003	2.139	1.287~3.555
疟疾史	无 No					1
History of malaria	有 Yes	-1.010	0.183	30.442	0.000	0.364	0.254~0.521
初诊结果	其他疾病 Other diseases					1
Initial diagnosis	疟疾 Malaria	-0.284	0.208	1.858	0.173	0.753	0.500~1.132
初诊到确诊时间间隔 Initial diagnosis to confirmation	0 d					1
	1~3 d	0.303	0.219	1.914	0.167	1.354	0.881~2.079
	> 3 d	0.751	0.269	7.808	0.005	2.120	1.252~3.591
疾病类型 Type of disease	非恶性疟 Non-falciparum malaria					1
疾病类型 Type of disease	恶性疟 Falciparum malaria	1.029	0.275	14.040	0.000	2.798	1.633~4.792
跨地区就诊 Cross- regional medical treatment	否 No					1
跨地区就诊 Cross- regional medical treatment	是 Yes	0.554	0.196	7.971	0.005	1.741	1.185~2.558