Comparative evaluation of the diagnosis, reporting and investigation of malaria cases in China, 2005-2014: Transition from control to elimination for the national malaria programme

Background: The elimination of malaria requires high-quality surveillance data to enable rapid detection and response to individual cases. Evaluation of the performance of a national malaria surveillance system could identify shortcomings which, if addressed, will improve the surveillance program for malaria elimination. Methods: Case-level data for the period 2005-2014 were extracted from the China National Notifiable Infectious Disease Reporting Information System and Malaria Enhanced Surveillance Information System. The occurrence of cases, accuracy and timeliness of case diagnosis, reporting and investigation, were assessed and compared between the malaria control stage (2005-2010) and elimination stage (2011-2014) in mainland China. Results: A total of 210 730 malaria cases were reported in mainland China in 2005-2014. The average annual incidence declined dramatically from 2.5 per 100 000 people at the control stage to 0.2 per 100 000 at the elimination stage, but the proportion of migrant cases increased from 9.8 % to 41.0%. Since the initiation of the National Malaria Elimination Programme in 2010, the overall proportion of cases diagnosed by laboratory testing consistently improved, with the highest of 99.0% in 2014. However, this proportion was significantly lower in non-endemic provinces (79.0%) than that in endemic provinces (91.4%) during 2011-2014. The median interval from illness onset to diagnosis was 3days at the elimination stage, with one day earlier than that at the control stage. Since 2011, more than 99% cases were reported within 1day after being diagnosed, while the proportion of cases that were reported within one day after diagnosis was lowest in Tibet (37.5%). The predominant source of cases reporting shifted from town-level hospitals at the control stage (67.9% cases) to city-level hospitals and public health institutes at the eliminate stage (69.4% cases). The proportion of investigation within 3days after case reporting has improved, from 74.6% in 2010 to 98.5% in 2014. Conclusions: The individual case-based malaria surveillance system in China operated well during the malaria elimination stage. This ensured that malaria cases could be diagnosed, reported and timely investigated at local level. However, domestic migrants and overseas populations, as well as cases in the historically malarial non-endemic areas and hard-to-reach area are new challenges in the surveillance for malaria elimination.