Changing epidemiology and challenges of malaria in China towards elimination

Abstract

Background: Historically, malaria had been a widespread disease in China. A national plan was launched in China in 2010, aiming to eliminate malaria by 2020. In 2017, no indigenous cases of malaria were detected in China for the first time. To provide evidence for precise surveillance and response to achieve elimination goal, a comprehensive study is needed to determine the changing epidemiology of malaria and the challenges towards elimination.

Methods: Using malaria surveillance data from 2011 to 2016, an integrated series of analyses was conducted to elucidate the changing epidemiological features of autochthonous and imported malaria, and the spatiotemporal patterns of malaria importation from endemic countries.

Results: From 2011 to 2016, a total of 21,062 malaria cases with 138 deaths were reported, including 91% were imported and 9% were autochthonous. The geographic distribution of local transmission have shrunk dramatically, but there were still more than 10 counties reporting autochthonous cases in 2013-2016, particularly in counties bordering with countries in South-East Asia. The importation from 68 origins countries had an increasing annual trend from Africa but decreasing importation from Southeast Asia. Four distinct communities have been identified in the importation networks with the destinations in China varied by origin and species.

Conclusions: China is on the verge of malaria elimination, but the residual transmission in border regions and the threats of importation from Africa and Southeast Asia are the key challenges to achieve and maintain malaria elimination. Efforts from China are also needed to help malaria control in origin countries and reduce the risk of introduced transmission.

Keywords: Africa; China; Elimination; Epidemiology; Importation; Malaria; Southeast Asia.

Fig. 1

Epidemic curve and demographic features of malaria in China. a Epidemic curve of autochthonous and imported malaria (n = 21,062) in China, 2011–2016. b Age of autochthonous male (n = 1223) and female cases (n = 685) in 2011–2016. c Age of imported male (n = 18,069) and female cases (n = 1085) in 2011–2016

Fig. 2

Geographic distribution of autochthonous and imported malaria by county in China, 2011 and 2016. Incidence rate of autochthonous malaria in a 2011 and b 2016. Incidence rate of imported malaria in c 2011 and d 2016

Fig. 3

Kernel density of autochthonous and imported malaria cases by species, 2011–2016. a Autochthonous P. vivax. b Imported Autochthonous P. vivax. c Autochthonous P. falciparum. d Imported P. falciparum

Fig. 4

The number of imported malaria cases reported in China and the incidence of malaria reported in each origin country, 2011–2016. The y-axis shows the log of number of malaria cases imported from different countries into China. The x-axis shows log of the annual average incidence rate reported in each country. This figure includes 65 countries with available incidence data reported in the World Malaria Report in 2017 [1]. The colours of points show the continents in where the countries are located

Fig. 5

Trend of imported Plasmodium malaria cases by origins and species, 2011–2016. a P. falciparum imported from Africa. b P. vivax imported from Africa. c P. falciparum imported from Southeast Asia. d P. vivax imported from Southeast Asia. The seasonality of imported cases was fitted by nonlinear regression with cosine function proposed in a previous study [32], and a linear regression model for the annual trend was fit with the equations provided

Fig. 6

Origin-destination networks and communities of malaria importation into China, 2011–2016. a The numbers and species of malaria imported from origins (68 countries) into destinations (31 provinces) in mainland China. b Four communities of the malaria importation networks. The proportion of Plasmodium species are presented for countries with ≥ 10 cases