Zoonotic diseases, especially those transmitted by arthropods such as mosquitoes, ticks, and sand flies, are an ongoing public health concern. Recently, two different zoonotic infections that may cause transfusion-transmitted infections have expanded their ranges and resulted in outbreaks. Babesiosis, a malaria-like illness transmitted by Ixodes ticks that is endemic to parts of the U.S. where testing is mandatory, was reported in Nova Scotia, Canada in 2023. Of 10,976 Nova Scotian blood donors screened for Babesia in 2025, one donor tested positive via a nucleic acid test (NAT), but positivity could not be confirmed upon follow-up screening. In addition, Western equine encephalitis virus (WEEV), which usually circulates among birds and small mammals via mosquitoes, spilled over, infecting over 1,500 horses and over 100 confirmed human cases in Argentina in 2023-2024. Rates of WEEV infection, however, were likely much higher, as the estimated symptomatic to asymptomatic ratio is 1:1,150 in adults. NAT screening of 4,048 whole blood donations from affected areas identified one viremic donor in the asymptomatic viral phase with sequence similarity to the circulating strains. The transfusion community must remain alert for emerging transfusion transmitted infections (TTIs) with flexible, locally informed strategies to reduce TTI risk.
References:
- Drews SJ, Charlton CL, Trecker MA, Bigham M, Bloch EM, Bruneau L, Coatsworth H, Conrod V, Cranney C, Goldman M, Hatchette TF, Kumaran D, McIsaac KE, Ndao M, Osmond L, Patriquin G, Ramirez-Arcos S, Todd L, Cram J, O’Brien SF, Pambrun C. Emergence of Babesiosis in Nova Scotia, Canada. NEJM Evid. 2026 Aug;5(8):EVIDpha2600131. doi: 10.1056/EVIDpha2600131. Epub 2026 Jul 28. PMID: 42517708.
- Blanco S, Frutos MC, Brenot K, Bustamante AG, Carrizo LH, Gallego SV. Western Equine Encephalitis Virus in Blood Donors during Outbreak, Argentina, 2023-2024. Emerg Infect Dis. 2026 Aug;32(8):1213–20. doi: 10.3201/eid3208.260078. PMID: 42521678; PMCID: PMC13426790.
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