Currently, the global malaria epidemic is still severe. China was certified malaria-free by WHO in 2021; however, there is a risk of cross-border importation and secondary transmission of malaria via aircrafts and through land bordering countries in China because of the complex environments in border areas between China and neighboring malaria-endemic countries, notably the explosive growth in the malaria epidemic in Myanmar in China-Myanmar border areas. This article summarizes typical cases of secondary transmission caused by imported malaria across the world, and proposes responses to cross-border importation and secondary transmission of malaria in non-border and border areas of China, in order to effectively reduce the risk of malaria importation and secondary transmission and consolidate the hard earned malaria elimination achievements.

There are still multiple challenges in China during the malaria post-elimination phase, including a large number of imported malaria cases with widespread distribution, low awareness of timely healthcare seeking, insufficient malaria diagnosis and treatment capacity of medical institutions and insufficient malaria surveillance and response capability of disease control and prevention institutions. As the core technical institutions for preventing the re-establishment of malaria transmission, both medical institutions and disease control and prevention institutions are required to enhance the collaboration between clinical and public health services, improve the malaria diagnosis and quality management system, intensify case identification and epidemiological investigations, and improve the management mechanism of antimalarial drug reserves. In addition, doctors are encouraged to become the main force in the health education and promotion of malaria prevention to improve the public health literacy. These approaches are recommended to improve the overall capability of timely identification, standardized treatment and effective response of imported malaria cases, so as to continuously consolidate the malaria elimination achievements in China.

Objective To establish a high-throughput method that can simultaneously, quickly, and accurately detect main malaria-transmitting Anopheles species and their resistance genes in China, providing a high-throughput monitoring tool for monitoring the main malaria vectors in China after malaria elimination. Methods In different sampling locations, including Tengchong City, Yunnan Province; Wenchang City, Hainan Province; and Donggang City, Liaoning Province, adult specimens of mosquitoes, including Anopheles sinensis, Anopheles minimus, Anopheles dirus, and Anopheles anthropophagus, were collected. Polymerase chain reaction (PCR) technology and Sanger sequencing were employed to detect the ITS2, kdr (L1014), rdl (A296), and ace-1 (G119) genes in individual mosquitoes. For the analysis of mixed samples, an optimized multiplex PCR reaction system, custom-designed dual barcode primers, and next-generation sequencing (NGS) technology were utilized to detect the aforementioned genes. The consistency was assessed using Kappa consistency tests and Chi-square tests for multiple rates. Sensitivity, specificity, and the Youden index were calculated using a four-grid table calculation method. The costs associated with each step of the normal operational process for each method were statistically summarized, and the optimal quantity of mixed samples for detection was determined by a comprehensive approach. Results Conventional PCR amplification of gDNA from 300 mosquitoes resulted in 144 individuals of Anopheles sinensis, 53 individuals of Anopheles dirus, 62 individuals of Anopheles anthropophagus, and 41 individuals of Anopheles minimus, as identified by Sanger sequencing. The mutation frequencies of resistance genes kdr (L1014), rdl (A296), and ace-1 (G119) were found in 73, 27, and 41 specimens, respectively. Using a newly established multiplex PCR reaction system based on custom dual barcode and NGS sequencing technology, samples corresponding to Sanger sequencing were detected under different sample sizes. The two methods showed high consistency in the results (all Kappa>0.900). Multiple comparison tests showed significant differences in the consistencies of the two methods across different sample sizes N (40, 80, 160), N (120, 200, 240, 280), and N (300) (χ2=26.547, P<0.001). The new method demonstrated high sensitivity and specificity across various sample sizes, with the Youden index ranging from highest to lowest as follows: 1 (40, 80, 160)>0.994 (120)>0.990 (280)>0.988 (200)>0.987 (240)>0.985 (300). With an increase in sample size from 40 to 300, the cost per sequencing site for the new method decreased from 20.0 yuan to 8.3 yuan, while the cost per sequencing site for the conventional method decreased from 16.7 yuan to 15.4 yuan. The optimal mixed sample size for the new method was determined to be 280. Conclusion The newly developed multiplex PCR and barcode NGS detection method enables simultaneous screening of four major malaria vector mosquito species and the presence of mutations in the ace-1, kdr, and rdl resistance genes, exhibiting excellent stability, high sensitivity, and specificity. It allows for the efficient analysis of large sample sizes in a single run, offering a cost-effective alternative compared to other types of detection methods.

Objective　To analyze the characteristics of the malaria epidemic and the indicators for "1-3-7" from 2021 to 2023 in China, understand the effectiveness and challenges in preventing re-establishment malaria in China, propose response strategies, and provide references for consolidating the achievements of malaria elimination. Methods　The individual malaria case data and focus data from 2021 to 2023 in the "Information System for Infectious Disease Surveillance" and the "Information System for Parasitic Diseases Prevention and Control" were collected, and epidemiological characteristics and indicators for “1-3-7” were analyzed. Results　From 2021 to 2023, a total of 4 132 malaria cases were reported in 31 provinces and Xinjiang Production and Construction Corps, with mainly falciparum malaria (59.2%, 2 445/4 132). The national malaria epidemic reached a historical low of 799 cases in 2021, before rebounding significantly to 2 488 cases in 2023. The top five provinces for malaria cases were Yunnan, Guangdong, Henan, Sichuan, and Shandong, accounting for 49.4% of the total (2 043/4 132) cases. Except for two long incubation cases infected with P. malariae and one non-mosquito-transmitted case, the remaining cases were imported from abroad, mainly from African countries (81.7%, 3 374/4 129), with P. vivax malaria mainly coming from Myanmar (63.7%, 638/1 001). Malaria cases mainly occur in middle-aged men and migrant overseas workers. 142 severe cases and 21 deaths of malaria were reported. 81.8% (3 378/4 132) of malaria cases sought medical attention within 3 days of symptom onset, and the initial diagnosis institutions were mainly county-level, municipal, and provincial hospitals(77.2%), with an accuracy malaria diagnosis rate of above 80.0%. The completion rates of the malaria indicators for "1-3-7" were all above 90.0%. Conclusions　Since the malaria elimination in China, there has been no re-establishment of malaria, and the surveillance response capability has been maintained at a high level. However, the epidemic of imported malaria continued to rise, severely endangering public health in China, especially in areas such as the China-Myanmar border where the risk of re-establishment was high. Currently, it is necessary to further enhance the awareness of the key populations about timely medical consultation for malaria, as well as healthcare workers' vigilance, diagnostic capabilities, and awareness of timely referrals. Efforts should be maintained to investigate and manage epidemics, strengthen prevention and control in key areas such as the China-Myanmar border in Yunnan, and continuously consolidate elimination achievements.

Abstract: Objective　Through analyzing the epidemiological characteristics of imported Plasmodium falciparum (P. falciparum) cases in China from 2017 to 2022, to understand the trend of imported P. falciparum epidemic before and after malaria elimination, and to provide data support for further prevention and control of imported P. falciparum. Methods　Epidemiological questionnaires of P. falciparum cases in 31 provinces (autonomous regions and municipalities directly under the Central Government, excluding Taiwan, Hong Kong, and Macao) and Xinjiang Production and Construction Corps were collected from the parasitic disease control information management system from 2017 to 2022, and the epidemic situation, overseas foci, and distribution of three were statistically analyzed. Results　From 2017 to 2022, a total of 7 026 cases of P. falciparum were reported nationwide, accounting for 64.2% (7 026/10 943) of the total number of cases, all of which were imported cases. The infected cases were distributed across 60 countries in 4 continents, mainly in African countries. P. falciparum was reported every month from 2017 to 2022, with uneven distribution throughout the year and a peak occurring at the beginning. The top five provinces with the highest number of P. falciparum malaria cases were Guangdong Province (13.1%, 922/7 026), Jiangsu Province (9.1%, 636/7 026), Shandong Province (8.1%, 569/7 026), Guangxi Zhuang Autonomous Region (7.6%, 537/7 026), and Zhejiang Province (7.6%, 534/7 026). The majority of cases were Chinese nationals (94.9%, 6 668/7 026), with a male-to-female ratio of 17.2∶1. Among the reported cases of P. falciparum, 239 were critically ill and 48 died. Conclusions　In the stage of preventing imported malaria retransmission, although all the reported malaria cases in China were imported cases, P. falciparum accounted for the high proportion. Considering the complexity and rapid progression of P. falciparum, which can lead to critical illness or even death, timely detection, accurate diagnosis and standardized treatment of malaria cases should be done to reduce critical illness or death.

In 2017, China achieved the target of zero indigenous malaria case for the first time, and has been certified as malaria free by World Health Organization in 2021. To further summarize the historical achievements and technical experiences of the elimination program, a project on the Roadmap Analysis and Verification for Malaria Elimination in China was carried out. Results of the project were compiled and published as the Atlas of Malaria Transmission in China (The Atlas). The Atlas using modern digital information technologies, has been supported by various data from 24 malaria endemic provinces of China since 1950, to assess the changes in malaria epidemic patterns from 1950 to 2019 at national and provincial levels. The Atlas is designed as two volumes, including a total of 1850 thematic maps and more than 130 charts, consisting of introductory maps, thematic maps of malaria epidemic and control at national and provincial levels. It objectively and directly shows the epidemic history, evolution process, and great achievements of the national malaria control and elimination program in China. The Atlas has important reference value for summing up historical experience in the national malaria elimination program of China, and malaria control and elimination in other endemic countries in the world.
Humans ; Malaria/prevention & control* ; China/epidemiology*

Abstract: As the scale and volume of China-African cooperation continue to expand, the opportunities inherent in China-African public health cooperation are also on the rise. Malaria prevention and control is one of the primary domains of China-African public health cooperation. Especially after China's elimination of malaria, incorporating China's experience into the local context to accelerate the control and elimination of malaria in Africa, is a critical scientific problem. This article retrospectively analyses the historical China-African cooperative projects on malaria prevention and control such as the artemisinin compound project for rapid clearance of malaria, the China-UK-Tanzania pilot project, and the institution-based network of China-Africa cooperation on malaria elimination (INCAM), cooperation with the World Health Organization, and the contribution of domestic non-governmental organizations. The article also examines the challenges faced in the China-African cooperation for controlling and eliminating malaria and envisions future cooperation directions.

With the gradual resumption of international travel, cross-border population movement has become frequent again, risk assessment of imported malaria has important public health significance to maintain malaria elimination status in China. Currently, risk index system construction method, risk index method, mathematical model method, and infectivity-receptivity- vulnerability method are mainly used in imported malaria risk assessment in China. This paper summarizes the common evaluation methods in the risk assessment of imported malaria research in China to provide references for the further research.

Malaria remains a global health challenge, although an increasing number of countries will enter pre-elimination and elimination stages. The prompt and precise diagnosis of symptomatic and asymptomatic carriers of Plasmodium parasites is the key aspect of malaria elimination. Since the launch of the China Malaria Elimination Action Plan in 2010, China has formulated clear goals for malaria diagnosis and has established a network of malaria diagnostic laboratories within medical and health institutions at all levels. Various external quality assessments were implemented, and a national malaria diagnosis reference laboratory network was established to strengthen the quality assurance in malaria diagnosis. Notably, no indigenous malaria cases have been reported since 2017, but the risk of re-establishment of malaria transmission cannot be ignored. This review summarizes the lessons about malaria diagnosis in the elimination phase, primarily including the establishments of laboratory networks and quality control in China, to better improve malaria diagnosis and maintain a malaria-free status. A reference is also provided for countries experiencing malaria elimination.
China/epidemiology* ; Clinical Laboratory Techniques ; Global Health ; Humans ; Laboratories ; Malaria/prevention & control*

The dihydrofolate reductase (dhfr) and dihydropteroate synthetase (dhps) genes of Plasmodium vivax, as antifolate resistance-associated genes were used for drug resistance surveillance. A total of 375 P. vivax isolates collected from different geographical locations in China in 2009-2019 were used to sequence Pvdhfr and Pvdhps. The majority of the isolates harbored a mutant type allele for Pvdhfr (94.5%) and Pvdhps (68.2%). The most predominant point mutations were S117T/N (77.7%) in Pvdhfr and A383G (66.8%) in Pvdhps. Amino acid changes were identified at nine residues in Pvdhfr. A quadruple-mutant haplotype at 57, 58, 61, and 117 was the most frequent (57.4%) among 16 distinct Pvdhfr haplotypes. Mutations in Pvdhps were detected at six codons, and the double-mutant A383G/A553G was the most prevalent (39.3%). Pvdhfr exhibited a higher mutation prevalence and greater diversity than Pvdhps in China. Most isolates from Yunnan carried multiple mutant haplotypes, while the majority of samples from temperate regions and Hainan Island harbored the wild type or single mutant type. This study indicated that the antifolate resistance levels of P. vivax parasites were different across China and molecular markers could be used to rapidly monitor drug resistance. Results provided evidence for updating national drug policy and treatment guidelines.
Antimalarials/pharmacology* ; China/epidemiology* ; Drug Combinations ; Drug Resistance/genetics* ; Folic Acid Antagonists/pharmacology* ; Humans ; Mutation ; Plasmodium vivax/genetics* ; Prevalence