关键词: 输入性疟疾, 流行特征, 浙江省

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