[Epidemiological features and diagnosis of malaria cases in Nantong City from 2015 to 2020]

To investigate the epidemiological characteristics and diagnosis of malaria cases in Nantong City from 2015 to 2020, so as to provide insights into the prevention of re-establishment of imported malaria and consolidation of malaria elimination achievements in the city.

The epidemic data of malaria in Nantong City from 2015 to 2020 were captured from the National Notifiable Disease Report System, the Information Management System for Parasitic Disease Control and individual epidemiological survey reports of malaria cases. The malaria parasite species, source of infections, population distribution, temporal distribution, spatial distribution and diagnosis of imported malaria cases were descriptively and statistically analyzed.

A total of 241 malaria cases were reported in Nantong City from 2015 to 2020, and all were overseas imported cases, including 191 cases with Plasmodium falciparum malaria (79.25%), 8 cases with P. vivax malaria (3.32%), 33 cases with P. ovale malaria (13.69%) and 9 cases with P. malaria malaria (3.73%). Overseas imported malaria cases acquired infections from 34 countries in Asia, Africa and Latin America, and 97.93% of the cases were infected in Africa, and 90.04% (217/241) were reported in Chongchuan District, Hai'an City and Haimen District. Imported malaria cases were aged from 20 to 68 years, and a median age of 45 (13) years, and 97.10% were male. The median duration between returning to China and malaria onset was 7 (9) days among all imported malaria cases, and the median duration from initial diagnosis to definitive diagnosis was 2 (2) days. There were 167 cases that were initially diagnosed as malaria, with a correct rate of 69.29%, and 53.53 (129/241) of malaria cases were diagnosed at city-level medical institutions and 41.49% (100/241) at county-level medical institutions. In addition, the proportion of malaria cases reported by city-level medical institutions increased from 39.62% in 2015 to 81.25% in 2020 (χ² = 6.94, P < 0.01).

The accuracy of initial malaria diagnosis requires to be improved in Nantong City. Malaria control knowledge should be specially given to migrant workers to shorten the duration of seeking medical care, and malaria training requires to be intensified among healthcare professionals to improve the diagnostic capability of imported malaria cases and the cure of severe P. falciparum malaria cases.