Risk factors associated with malaria infection along China-Myanmar border: a case-control study.

BACKGROUND: The World Health Organization (WHO) has certificated China malaria free, but imported malaria is a continuous challenge in preventing reintroduction of malaria in the border area of China. Understanding risk factors of malaria along China-Myanmar border is benefit for preventing reintroduction of malaria in China and achieving the WHO's malaria elimination goal in the Greater Mekong Subregion (GMS). METHODS: This is a case-control study with one malaria case matched to two controls, in which cases were microscopy-confirmed malaria patients and controls were feverish people with microscopy-excluded malaria. A matched logistic regression analysis (LRA) was used to identify risk factors associated with malaria infection. RESULTS: From May 2016 through October 2017, the study recruited 223 malaria cases (152 in China and 71 in Myanmar) and 446 controls (304 in China and 142 in Myanmar). All the 152 cases recruited in China were imported malaria. Independent factors associated with malaria infection were overnight out of home in one month prior to attendance of health facilities (adjusted odd ratio [AOR] 13.37, 95% confidence interval [CI]: 6.32-28.28, P < 0.0001), staying overnight in rural lowland and foothill (AOR 2.73, 95% CI: 1.45-5.14, P = 0.0019), staying overnight at altitude < 500 m (AOR 5.66, 95% CI: 3.01-10.71, P < 0.0001) and streamlets ≤ 100 m (AOR9.98, 95% CI: 4.96-20.09, P < 0.0001) in the border areas of Myanmar; and people lacking of knowledge of malaria transmission (AOR 2.17, 95% CI: 1.42-3.32, P = 0.0004). CONCLUSIONS: Malaria transmission is highly focalized in lowland and foothill in the border areas of Myanmar. The risk factors associated with malaria infection are overnight staying out of home, at low altitude areas, proximity to streamlets and lack of knowledge of malaria transmission. To prevent reintroduction of malaria transmission in China and achieve the WHO goal of malaria elimination in the GMS, cross-border collaboration is continuously necessary, and health education is sorely needed for people in China to maintain their malaria knowledge and vigilance, and in Myanmar to improve their ability of personal protection.