Spatio-temporal analysis of malaria vectors in national malaria surveillance sites in China.

BACKGROUND: To reveal the spatio-temporal distribution of malaria vectors in the national malaria surveillance sites from 2005 to 2010 and provide reference for the current National Malaria Elimination Programme (NMEP) in China. METHODS: A 6-year longitudinal surveillance on density of malaria vectors was carried out in the 62 national malaria surveillance sites. The spatial and temporal analyses of the four primary vectors distribution were conducted by the methods of kernel k-means and the cluster distribution of the most widely distribution vector of An.sinensis was identified using the empirical mode decomposition (EMD). RESULTS: Totally 4 species of Anopheles mosquitoes including An.sinensis, An.lesteri, An.dirus and An.minimus were captured with significant difference of distribution as well as density. An. sinensis was the most widely distributed, accounting for 96.25% of all collections, and its distribution was divided into three different clusters with a significant increase of density observed in the second cluster which located mostly in the central parts of China. CONCLUSION: This study first described the spatio-temporal distribution of malaria vectors based on the nationwide surveillance during 2005-2010, which served as a baseline for the ongoing national malaria elimination program.

Changing malaria transmission and implications in China towards National Malaria Elimination Programme between 2010 and 2012.

BACKGROUND: Towards the implementation of national malaria elimination programme in China since 2010, the epidemiology of malaria has changed dramatically, and the lowest malaria burden was achieved yearly. It is time to analyze the changes of malaria situation based on surveillance data from 2010 to 2012 to reconsider the strategies for malaria elimination. METHODS AND PRINCIPAL FINDINGS: Malaria epidemiological data was extracted from the provincial annual reports in China between 2010 and 2012. The trends of the general, autochthonous and imported malaria were analyzed, and epidemic areas were reclassified according to Action Plan of China Malaria Elimination (2010-2020). As a result, there reported 2743 malaria cases with a continued decline in 2012, and around 7% autochthonous malaria cases accounted. Three hundred and fifty-three individual counties from 19 provincial regions had autochthonous malaria between 2010 and 2012, and only one county was reclassified into Type I (local infections detected in 3 consecutive years and the annual incidences ≥ 1/10,000) again. However, the imported malaria cases reported of each year were widespread, and 598 counties in 29 provinces were suffered in 2012. CONCLUSIONS/SIGNIFICANCE: Malaria was reduced significantly from 2010 to 2012 in China, and malaria importation became an increasing challenge. It is necessary to adjust or update the interventions for subsequent malaria elimination planning and resource allocation.

[Malaria situation in the People's Republic of China in 2011].

Totally 4 479 malaria cases were reported through the annual reporting system from 782 counties of 27 Provinces/ Municipalities/Autonomous Regions (P/M/A) in 2011, this created a new-low number representing 43.0% reduction compared with 7 855 cases in 2010, and accordingly the annual incidence was reduced to 0.033 4/10 000. However, the number of malaria deaths increased to 33 from 19 in 2010. Among the 782 counties with reported cases, 2 counties of Motuo (16.466 0/10 000) in Tibet and Ruili (12.235 2/ 10000) in Yunnan had an incidence of more than 10/10 000, 10 counties in Yunnan and 1 county in Guizhou had an incidence between 1/10 000 and 10/10 000, and that of the others was below 1/10 000. The malaria areas and transmission got further confined than in 2010. Out of the 4 479 malaria cases, a proportion of 29.3% was reported as the indigenous cases who mainly distributed in the provinces of Anhui (40.0%), Yunnan (25.8%), Henan (12.6%), Guizhou (10.4%) and Hubei (6.1%), a proportion of 66.4% was reported as the abroad-imported cases who mainly distributed in Yunnan (36.5%), Jiangsu (12.0%), Henan (6.2%), Sichuan (5.8%) and Hunan (4.8%), and the remaining 4.3% were domestically-mobile cases. Meanwhile, the confirmed cases took 81.7% while the other 18.3% were clinically diagnosed cases. Among the confirmed cases, 56.7% were Plasmodium vivax cases reported from 25 provinces, 40.2% were P. falciparum cases reported from 22 provinces, 1.1% were mixed infections of P. vivas and P. falciparum reported from 10 provinces, and the remaining 1.9% were P. malariae or P. ovale cases reported from 14 provinces. The 32 indigenous falciparum malaria cases were found only in Yunnan Province. Yunnan was still the major malaria province which ranked No.1 in the country in terms of the case number, 1 522 cases representing 42.4% decrease of the last year with an incidence of 0.331 4/10 000. Among the cases, 301 were falciparum malaria accounting for 20.3% of the national falciparum malaria figure. As previous key malaria province however, Hainan reported only 9 malaria cases indicating 88.5% decrease of the last year with an incidence of 0.010 4/ 10 000, and ranked down to No. 25. In central China, another major malaria region, the case number decreased considerably. However, Anhui still reported 644 malaria cases though with a decrease of 65.5% in comparison to that of 2010, ranked No. 2, accounting for 14.4% of the country's malaria cases with an incidence of 0.100 0/10 000. In Jiangsu, 374 cases were reported and decreased by 3.1% with an incidence of 0.050 8/10 000. In Henan, the number of reported cases was 358 and decreased by 59.9% with an incidence of 0.038 7/10 000. In Hubei, 167 malaria cases were reported and decreased by 61.1% with an incidence of 0.027 7/10 000. Cases reported from other provinces occupied 31.4% of the total. Respectively from Guizhou, Sichuan, Guangxi, Guangdong, Zhejiang, Hunan and Shandong provinces, 100-200 malaria cases were reported; and the number of cases was less than 100 in the provinces of Fujian, Chongqing, Shanghai, Hebei, Beijing, Tianjin, Xinjiang, Ningxia, Jiangxi, Liaoning, Shaanxi, Shanxi, Gansu and Tibet. Although a delightful progress was made with a substantial reduction of malaria transmission, China had to face the following challenges relating to malaria endemic situation: 1) Malaria cases appeared in almost one thousand counties in most provinces and nearly 200 counties reported indigenous cases. In some counties the transmission is still high, and it is still critical for the provinces of Anhui, Yunnan, Henan, Guizhou, Hubei and Tibet to interrupt the local malaria transmission. 2) Imported malaria cases were dominant and widely distributed in the country including the 4 plasmodium species, this could bring about high risks of re-introduction of malaria transmission in areas where malaria was effectively under control, particularly could cause more malaria deaths in the circumstances of increased imported falciparum malaria cases, therefore provinces with more mobile population and imported cases need to pay higher attention. 3) A number of clinically diagnosed but unconfirmed cases still exist in malaria elimination stage which need to be addressed through strengthening local laboratory diagnosis capabilities.