From malaria elimination to post-elimination: a 10-year surveillance data study in Shanghai

Background The aim of this study was to investigate and analyse the characteristics of malaria in Shanghai from 2010 to 2019 and to provide suggestions for areas with a similar elimination process in China in order to prompt development of strategies and interventions in the post-elimination stage. Methods This was a cross-sectional study exploring the malaria characteristics during 2010-2019 in Shanghai, China. Malaria data from the Infectious Diseases Information Reporting Management System (IDIRMS) between 2010 and 2012 and data from the Parasitic Diseases Information Reporting Management System (PDIRMS) between 2013 and 2019 were combined for analysis in this study. Results From 2010 to 2019, a total of 436 malaria cases were reported in Shanghai. Among them, 415 (95.18%) were imported from abroad, 19 (4.36%) were domestically acquired from other provinces, 1 (0.23%) case was caused by blood transfusion, and 1 (0.23%) had a long incubation. Only Plasmodium vivax was found in domestically indigenous cases; Plasmodium falciparum accounted for the largest proportion of imported cases. Domestically acquired cases were only reported in 2010-2011 and 88% occurred in June to September; no significant seasonal difference was observed for imported cases over the 10 years. No local transmission has occurred in Shanghai since 2012. The median interval from fever onset to diagnosis was 3 days. Between 2010 and 2019, among 308 foci, 33 were classified as potential transmission and dispersed in suburb areas (Minhang, Baoshan, Jiading, Pudong, Jinshan, Songjiang, Qingpu, Fengxian, and Chongming). Only Anopheles sinensis was present and the proportion of Anopheles sinensis in different species of mosquitoes under surveillance in Shanghai decreased from 2011 to 2019. Conclusions Shanghai faces the challenge of malaria re-establishment caused by imported malaria in the post-elimination stage. Therefore, risk investigation and assessment should be carried out, and receptivity and susceptibility should be assessed for every point of focus. Training should be continued to strengthen facility staff capability, and multisectoral coordination and cooperation need to be conducted efficiently to maintain malaria elimination in Shanghai.

Automated summary

Shanghai has not had any local transmission of malaria since 2012, with the majority of cases being imported. Domestically acquired cases were mainly reported in 2010-2011 and occurred predominantly in June to September. Shanghai faces the challenge of malaria re-establishment caused by imported cases.