Abstract:

Objective To analyze the epidemiological characteristics of malaria cases reported in Shanghai Public Health Clinical Center to provide scientific basis for surveillance and prevention malaria of imported in the pos-elimination phase. Methods Data of the malaria cases from 2012 to 2022 were collected from the information management system of Shanghai Public Health Clinical Center and analyzed using descriptive statistical method on the infected species, source of infection, triple distribution, and clinical visits and diagnosis. Results The results showed that a total of 248 malaria cases were reported in Shanghai Public Health Clinical Center during 2012—2022, and all cases were imported from overseas. There were 228 patients of Chinese nationality (91.9%) and 20 patients were foreigners (8.1%). The most cases were Plasmodium falciparum infection (208 cases, 83.9%). The highest number of cases was seen in 2017. The infecting cases were mostly imported from African countries (229 cases, 92.3%) and others were from Asian (13 cases, 5.2%)， South American countries (1 case, 0.4%) and unkown area (5 cases, 2.0%). There were cases reported in every month, and there was no seasonal pattern on the number of imported cases. The regional distribution of imported cases showed that 126 cases were located out of Shanghai, 114 cases were in Shanghai. There were 8 cases unknown. Pudong New Area (24 cases, 21.1%), Minhang District (14 cases, 12.3%) and Songjiang District (11 cases, 9.6%) had the highest number of cases in Shanghai. The reported malaria cases comprised 234 males (94.4%) and 14 females (5.6%), with a male-to-female ratio of 17 ∶ 1. The age of the cases were mainly in the age groups of 20-49 years (203 cases, 81.9%). The occupational background of the cases was dominated by migrant workers (187 cases, 75.4%). The number of cases treated at non-Shanghai hospitals and Shanghai hospitals were 14 and 234 cases, respectively. The malaria successful diagnosis rate was 96.3% (154/160) in tertiary A-level hospital, and 81.1% (60/74) in lower medical institutions during 2012—2022 in Shanghai. According to the 248 malaria cases, the average time period from the onset of symptoms to initial examination was 4.5 days, with a median of 2 (0，4) d. Of the Shanghai cases, 189 cases (76.2%) had initial examination 3 days after the onset of symptoms, 51 cases (20.6%) had that 4-10 days after the onset of symptoms, and 8 cases (3.2%) had that 10 days after the onset of symptoms. There was a significant difference between the median time from onset of symptoms to initial examination of malaria (F = 6.393, P < 0.05). The mean time intervals from initial examination to diagnosis was 1.2 d, and the median was 1 (0, 2) d. Of these cases, 112 patients were diagnosed on the day of first examination; 223 cases were diagnosed within 3 days after the initial exminatio and 25 were diagnosed more than 3 days after the initial examination. There was no significant difference between the median time from first examination to diagnosis (F = 1.24, P > 0.05). Conclusion The malaria cases reported in Shanghai Public Health Clinical Center from 2012 to 2022 were all imported from abroad with the dominant species of P. falciparum. The infection source was mainly from African countries. It is urged that Shanghai should continuously strengthen the surveillance and management of imported malaria, enhance the capability of diagnosis and clinical care in medical institutions, and strengthen health education for outbound personnel to consolidate the achievements of malaria elimination.

Key words: Malaria, Imported cases, Epidemiological characteristic, Shanghai