Abstract: Objective To compare the screening effects of RDT, microscopy and PCR for malaria among residents in low malaria areas and elimination areas, and to investigate the presence of malaria in residents of border Villages in Cangyuan Va County and asymptomatic infections in surrounding areas, providing a basis for preventing re-introduction of malaria after elimination. Methods From August 2020 to March 2021, the fingertip blood of the investigated subjects was collected from three survey sites in the border area between China and Myanmar, namely Banlao Township in Cangyuan Va Autonomous County of Lincang City, Banwai District, Mengmao County, the Second Special Zone of Shan State, Myanmar, Yongmo and Dayan Township, Nandeng Special Zone, the Second Special Zone of Shan State, Myanmar. The malaria parasite antigen detection test kit, malaria parasite microscopic examination, fluorescent quantitative PCR and nested PCR were used to detect the asymptomatic infection of malaria parasites. Results A total of 1 040 blood samples were collected, including 606 from China and 434 from Myanmar, with 506 males and 534 females. Among them, , there were 51 individuals aged 0 to <5 years, 283 aged 5 to < years, 187 aged 15 to < years, 232 aged 30 to <45 years, 205 aged 45 to < years, and 82 aged ≥60 years. All 1 040 people tested negative for plasmodium antigen detection kit. One case of Plasmodium vivax detected by plasmodium microscopic etiology, with a detection rate of 0.10%. One case of P. vivax was also detected by fluorescent quantitative PCR and nested PCR, with a detection rate of 0.10%. Among them, one case of P. vivax was detected in Banwai District, Mengmao County, the Second Special Zone of Shan State, Myanmar, with a detection rate of 0.35%. The detection rates of malaria parasites in Banlao Township in Cangyuan Va Autonomous County of Lincang City, Yunnan Province and Yongmo Township and Dayan Township, Nandeng Special District, the Second Special Zone of Shan State, Myanmar were both 0. The difference in the detection rate of malaria parasites among the three survey sites was not statistically significant (χ2 =2.682, P>0.05). The asymptomatic P. vivax infection was detected in a 6-year-old girl from Banwai District, Mengmao County, the Second Special Zone of Shan State, Myanmar. Conclusions RDT is not suitable for malaria screening in low malaria area and elimination area. Microscopic examination and PCR can be used for malaria screening, but PCR operation is complex and costly. In surrounding areas outside of China, malaria is still prevalent, while there is no source of malaria infection in border villages of Cangyuan Va County. However, there is a risk of importation, and timely and effective measures should be taken to prevent reintroduction and transmission.

Recently, malaria incidence has sharply resurgence in the border area of northern Myanmar, with the parasite incidence rate in 2023 being 21.47 times (95% CI: 18.84-24.48) that of 2019 in Kachin State's Razan and nearby areas. This resurgence caused the number of imported malaria cases to increase from 188 in 2019 to 398 in 2023 in Yunnan Province. In addition to the impact of military conflict, the border malaria joint prevention and control cooperation mechanism and malaria control measures established between China and Myanmar have failed to be implemented effectively due to the impact of the international COVID-19 epidemic. Hence, it is recommended that relevant departments evaluate the quality and effectiveness of the current cross-border transmission measures for malaria in the China-Myanmar border area from a technical perspective, and provide a large demand for primaquine, which can block the spread of malaria and cure vivax malaria, in response to the current prevalent characteristics of vivax malaria predominating in northern Myanmar. Moreover, to effectively reduce the mortality of imported malaria patients and prevent re-importation and transmission, it is necessary to enhance clinical physicians' knowledge, awareness, and vigilance regarding malaria diagnosis and treatment in the Yunnan border region, as well as China's ability and quality of appropriate response to imported malaria.