Microgeographic Heterogeneity of Border Malaria During Elimination Phase, Yunnan Province, China, 2011-2013.

Malaria, one of the most devastating infectious diseases, creates an enormous public health burden in the developing world (1). Since 2000, increased financial support has strengthened malaria control programs, leading to substantially reduced malaria incidence and death rates, even in the high-transmission areas of sub-Saharan Africa (1). The estimated worldwide malaria death rate declined by 45% during 2000–2012. Of the 97 countries with malaria transmission in 2013, twelve are in the preelimination phase and 7, including China, are in the elimination phase. In early 2009, China’s Ministry of Health presented its Revised National Malaria Strategy 2010–2015; this strategy was followed by the Malaria Elimination Action Plan for 2010–2020, in which the Ministry of Health laid out a strategy to eliminate malaria by 2020 (2,3). Control efforts, guided by the 1–3-7 strategy (reporting a malaria case within 1 day; confirming, treating, and investigating the case within 3 days; and delivering an appropriate public health response to prevent further transmission within 7 days) have drastically reduced malaria incidence in central China (4). As a result, malaria transmission is restricted to the southwestern Yunnan Province along the international borders (5–8). Currently, Plasmodium vivax is the predominant species of malaria parasites in China, and autochthonous P. falciparum occurs only in Yunnan Province (7,8). In 2012, Yunnan Province reported an annual malaria incidence of 7.4 cases/100,000 population (8). Yunnan Province borders 3 malaria-endemic countries: Myanmar, Laos, and Vietnam. Previous studies found that cross-border migration from Myanmar was the major source of importation/reintroduction of P. falciparum malaria in Yunnan Province (9). Therefore, the control strategy during the elimination phase must focus on eliminating local transmission and cross-border introduction. Elimination strategies can differ profoundly from control strategies because they require prospective, accurate identification of transmission foci and rapid control responses (10–13). Earlier studies in China relied exclusively on retrospective data acquired from county-level hospital records (5–8). The retrospective nature of these studies raises questions about diagnostic accuracy, whereas the county-level epidemiologic data provide limited spatial resolution. A county in China typically comprises many townships, sometimes ≈100 villages and totaling ≈1 million persons, and it might span ≈100 km (14–17), which limit the usefulness of county-level risk assessment for guiding targeted malaria control and local malaria elimination. Thus, for spatially heterogeneous malaria transmission, finer-scale mapping is essential for deploying elimination measures. We aimed to use prospectively confirmed malaria data to identify high-risk foci of malaria transmission at the township level in Yunnan Province along the international border. Specifically, we wanted to locate the transmission hot spots and determine whether malaria transmission is heterogeneous at the township level. Our goal was to provide data to help guide targeted malaria control response during the malaria elimination phase.