Objective:To analyze the epidemiological characteristics and prevention measures of imported malaria cases in Chenzhou City, and to provide a basis for improving the monitoring and response system after malaria elimination and consolidating the achievements of malaria elimination.Methods:A retrospective analysis was conducted to collect data on imported malaria cases in Chenzhou City from 2017 to 2023 from the Chinese Disease Prevention and Control Information System and Parasitic Disease Information Management System. The three-dimention distribution patterns of malaria cases (population, time, and region distribution) were described. The results of investigation and handling of cases, monitoring of malaria vectors, and the quality of blood slides were evaluated and analyzed.Results:A total of 24 imported malaria cases were reported in Chenzhou City from 2017 to 2023, with an average annual incidence rate of 0.07/100 000. No secondary cases or deaths were reported. Among them, there were 23 imported cases and 1 transfusion infection case. Falciparum malaria was the main cause, accounting for 66.67% (16/24) of the total cases. The main source of infection was African countries, accounting for 91.67% (22/24). Among the 24 cases of imported malaria, there were 22 males and 2 females, with a gender ratio of 11.00 ∶ 1.00. The age of onset was mainly concentrated 40 - 59 years old, accounting for 70.83% (17/24). The occupational distribution was mainly composed of overseas workers (mining, metallurgy, road construction, etc.), accounting for 66.67% (16/24). The highest number of cases occurred in February and December, both accounting for 16.67% (2/24). In terms of regional distribution, except for Linwu County, Guidong County, and Anren County, all other counties (cities, districts) had reported cases, with Beihu District accounting for the highest proportion (33.33%, 8/24). The implementation rate of the work norms for eliminating malaria "1-3-7" was 100%, and the time from onset to diagnosis [ M ( Q1, Q3)] was 1 (0, 3) d. The diagnostic units were mainly medical institutions at or above the city level, accounting for 75.00% (18/24) of the total cases. There was a statistically significant difference in the proportion of malaria cases diagnosed institutions at all levels (χ 2 = 29.63, P < 0.001). A total of 495 Anopheles were captured for monitoring the population of malaria vector mosquitoes, and 1 311 Anopheles were captured for monitoring the density of malaria vector mosquitoes, all of which were Anopheles sinensis, and the monitoring density was 1.49 per person per hour. A total of 18 940 fever patients underwent blood tests, and 884 negative blood slides were rechecked for quality. The qualified rates of blood slide production, staining, and cleanliness were statistically significant differences in different years (χ 2 = 19.91, 47.59, 71.15, P < 0.05). Conclusions:The imported malaria cases in Chenzhou City are mainly Falciparum malaria, and the infection sources are mostly African countries. The affected population is mainly middle-aged male overseas workers, and the onset time is higher in February and December. The cases are mainly distributed in Beihu District. Meanwhile, the quality of malaria parasite blood slides from fever patients and the diagnostic capabilities of medical institutions at all levels need to be improved. The case monitoring, publicity and education for key populations, and grassroots capacity building should be strengthened to prevent the risk of malaria reintroduction.

Objective:To analyze the epidemiological characteristics and prevention measures of imported malaria cases in Chenzhou City, and to provide a basis for improving the monitoring and response system after malaria elimination and consolidating the achievements of malaria elimination.Methods:A retrospective analysis was conducted to collect data on imported malaria cases in Chenzhou City from 2017 to 2023 from the Chinese Disease Prevention and Control Information System and Parasitic Disease Information Management System. The three-dimention distribution patterns of malaria cases (population, time, and region distribution) were described. The results of investigation and handling of cases, monitoring of malaria vectors, and the quality of blood slides were evaluated and analyzed.Results:A total of 24 imported malaria cases were reported in Chenzhou City from 2017 to 2023, with an average annual incidence rate of 0.07/100 000. No secondary cases or deaths were reported. Among them, there were 23 imported cases and 1 transfusion infection case. Falciparum malaria was the main cause, accounting for 66.67% (16/24) of the total cases. The main source of infection was African countries, accounting for 91.67% (22/24). Among the 24 cases of imported malaria, there were 22 males and 2 females, with a gender ratio of 11.00 ∶ 1.00. The age of onset was mainly concentrated 40 - 59 years old, accounting for 70.83% (17/24). The occupational distribution was mainly composed of overseas workers (mining, metallurgy, road construction, etc.), accounting for 66.67% (16/24). The highest number of cases occurred in February and December, both accounting for 16.67% (2/24). In terms of regional distribution, except for Linwu County, Guidong County, and Anren County, all other counties (cities, districts) had reported cases, with Beihu District accounting for the highest proportion (33.33%, 8/24). The implementation rate of the work norms for eliminating malaria "1-3-7" was 100%, and the time from onset to diagnosis [ M ( Q1, Q3)] was 1 (0, 3) d. The diagnostic units were mainly medical institutions at or above the city level, accounting for 75.00% (18/24) of the total cases. There was a statistically significant difference in the proportion of malaria cases diagnosed institutions at all levels (χ 2 = 29.63, P < 0.001). A total of 495 Anopheles were captured for monitoring the population of malaria vector mosquitoes, and 1 311 Anopheles were captured for monitoring the density of malaria vector mosquitoes, all of which were Anopheles sinensis, and the monitoring density was 1.49 per person per hour. A total of 18 940 fever patients underwent blood tests, and 884 negative blood slides were rechecked for quality. The qualified rates of blood slide production, staining, and cleanliness were statistically significant differences in different years (χ 2 = 19.91, 47.59, 71.15, P < 0.05). Conclusions:The imported malaria cases in Chenzhou City are mainly Falciparum malaria, and the infection sources are mostly African countries. The affected population is mainly middle-aged male overseas workers, and the onset time is higher in February and December. The cases are mainly distributed in Beihu District. Meanwhile, the quality of malaria parasite blood slides from fever patients and the diagnostic capabilities of medical institutions at all levels need to be improved. The case monitoring, publicity and education for key populations, and grassroots capacity building should be strengthened to prevent the risk of malaria reintroduction.