Heightened non-testing risk mitigation blood donor screening with retrospective transcription-mediated amplification testing during a 2023 local Florida malaria cluster

BackgroundTransfusion-transmitted malaria risk in the USA is estimated at less than one per ten million blood donations or about 1 case every 2 years. A total of 18 autochthonous malaria infections have been reported in the USA since 2003: eight cases in 2003 and ten cases in 2023 with fifteen reported from Florida. From May to July 2023 in Sarasota County, Florida, symptomatic P. vivax malaria was detected in seven individuals with no recent malaria travel history. Study Design and MethodsIn the absence of an FDA-approved blood donor screening test for malaria at the time, the local blood center responded to this 2023 cluster by implementing a non-testing risk mitigation strategy of escalating blood donor screening measures and pathogen reduction. Potential blood supply safety enhancement by use of additional nucleic acid testing (NAT) on samples from donors in impacted areas was studied retrospectively using the Procleix Plasmodium Assay, a transcription-mediated amplification detecting five human Plasmodium species 18S ribosomal RNA with a limit of detection ranging from 2-7 infected erythrocytes per mL. ResultsAmong the 435 valid study samples from accepted healthy blood donors, screened with heightened non-testing measures in the 4-6 mile radius of malaria-impacted area, all samples were nucleic acid test non-reactive. DiscussionThe blood center strategy in response to the local 2023 malaria outbreak maintained the blood supply safety with no transfusion-transmitted malaria and no retrospective evidence of Plasmodium in the 435 valid samples collected from blood donors residing in impacted areas.