关键词: 重症病例, 输入性疟疾, 流行病学特征, 影响因素

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