[Epidemiological characteristics of imported malaria in Zhengzhou City from 2016 to 2020]

To analyze the epidemiological characteristics of reported imported malaria cases in Zhengzhou City from 2016 to 2020, so as to provide insights into the management of imported malaria in the city.

All data pertaining to cases with definitive diagnosis of malaria in Zhengzhou City from 2016 to 2020 were captured from the National Notifiable Disease Report System and the Information Management System for Parasitic Disease Control in China, including individual demographic data, and malaria onset, initial diagnosis and definitive diagnosis data. All data were descriptively analyzed. The duration from malaria onset to initial diagnosis, from initial diagnosis to definitive diagnosis and from onset to definitive diagnosis was compared among cases. In addition, the diagnoses of imported malaria cases in which definitive diagnosis was made were compared with the reexaminations by Zhengzhou Municipal Malaria Diagnosis Reference Laboratory.

A total of 302 cases with definitive diagnosis of malaria were reported in Zhengzhou City from 2016 to 2020, and all were imported cases, with Plasmodium falciparum malaria as the predominant type (230 cases, 76.2%). There were 293 malaria cases imported from Africa (293 cases, 97.0%), which mainly included Nigeria (48 cases, 15.9%), Angola (40 cases, 13.2%), and the Democratic Republic of the Congo (29 cases, 9.6%). There was no obvious seasonality found in the date of malaria onset and time of reporting malaria. The ratio of male to female malaria cases was 49.3:1, and there were 103 cases (34.1%) with the current residency address in Zhengzhou City, 193 cases (63.9%) with the current residency address in other cities of Henan Province and 6 cases (2.0%) in other provinces of China. There were 271 cases (89.7%) seeking initial diagnosis in medical institutions, and the diagnostic accuracy of malaria was 56.6% (171/302) at initial diagnosis institutions. A total of 122 cases (40.4%) sought medical care on the day of malaria onset, and 252 cases (86.4%) within 3 days; however, only 22 cases (7.3%) were definitively diagnosed on the day of onset, and 162 cases (53.6%) diagnosed within 3 days. There were no significant differences between malaria cases seeking initial diagnosis at medical institutions and disease control and prevention institutions in terms of the duration from malaria onset to initial diagnosis (Z = -1.663, P > 0.05), from initial diagnosis to definitive diagnosis (Z = -0.413, P > 0.05) or from malaria onset to definitive diagnosis (Z = -0.838, P > 0.05). The median duration (interquartile range) from initial diagnosis to definitive diagnosis of malaria was 3.00 (2.00), 3.00 (6.00), 2.00 (4.00) d and 1.00 (1.00) d among cases seeking medical care at township-level and lower, county-, city- and province-level medical institutions, and the median duration from initial diagnosis to definitive diagnosis of malaria was significantly longer among cases seeking medical care at township-level and lower medical institutions than at city (Z = -3.286, P < 0.008 33) and province-level medical institutions (Z = -9.119, P < 0.008 33), while the median duration from initial diagnosis to definitive diagnosis [1.00 (3.00) d vs. 2.00 (4.00) d; Z = -4.099, P < 0.016] and from malaria onset to definitive diagnosis [3.00 (4.00) d vs. 4.00 (5.00) d; Z = -2.868, P < 0.016] among malaria cases with the current residency address in Zhengzhou City was both shorter than in other cities of Henan Province. The diagnostic accuracy was 89.1% (269/302) among malaria cases in which definitive diagnosis was made, and the accuracy of malaria reexaminations was 94.0% (284/302) in Zhengzhou Municipal Malaria Diagnosis Reference Laboratory.

P. falciparum malaria was predominant among reported imported malaria cases in Zhengzhou City from 2016 to 2020, and these imported malaria cases were predominantly diagnosed at medical institutions; however, the diagnostic capability of malaria is poor in township-level and lower medical institutions. Strengthening the collaboration between medical institutions and disease control and prevention institutions and improving the diagnostic capability building at medical institutions are recommended to consolidate malaria elimination achivements.