Cooperative Sentinel Surveillance of Malaria in Laiza and Nearby Areas of Myanmar and Importation Threat Monitoring—China,2019–2023

Introduction:Laiza and nearby areas(LNA)in Myanmar are identified as the primary malaria hotspots in the bordering regions of Yunnan Province,China.Methods:Six sentinel surveillance sites were established at the China-Myanmar border in LNA to monitor malaria.Data from 2019 was used as a baseline to analyze malaria incidence and trends in LNA and Myanmar,as well as the importation of malaria cases into China from 2019 to 2023.Results:Plasmodium vivax was the predominant species,representing 99.95%(14,060/14,066)of confirmed malaria cases in LNA.A total of 8,356 malaria cases were identified in 2023,with an annual parasite incidence(API)of 19.78 per 100 person-years.Compared to 2019,the incidence rate ratio was 21.47(95%confidence interval:18.84,24.48),indicating that the API in 2023 was 21.47 times higher than that in 2019.In Yunnan,out of 1,016 reported cases,545 imported cases(53.64%)originated from LNA and spread to 18(13.95%)out of 129 counties.Ten provinces in China,including Yunnan,reported imported malaria cases from LNA in Myanmar.Conclusions:The increase in population,particularly among internally displaced persons,along with inadequate healthcare services,has led to a notable resurgence of malaria in LNA.This resurgence poses a risk to preventing the re-emergence of malaria transmission in China.There is an urgent need for novel collaborative policies,as well as financial and technical assistance,to enhance malaria control efforts in LNA,Myanmar.

Prevalence of antifolate drug resistance markers in Plasmodium vivax in China

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.