In Focus
Emerging arboviral infections and blood safety
Why are arboviruses relevant to blood safety?
Arboviruses (viruses transmitted by arthropods, particularly mosquitoes and ticks) represent a growing challenge for blood safety.
The geographical distribution of arboviruses can change rapidly as a result of climate change and international travel. Approximately 5.7 billion people live in regions suitable for arbovirus transmission and these viruses are expanding into new regions1. Humans are primarily infected through the bite of an infected mosquito or tick although transmission can occur through blood transfusion as well2. Some arboviruses survive the processing and storage of different blood components.
Most arboviral infections are asymptomatic and can be associated with transient viraemia, resulting in the possibility that infected donors may present to donate blood without recognising that they are infected. Therefore, it is not possible to reliably defer individuals with arbovirus infections from blood donation based on symptoms alone. However, arboviral infections can be severe in high-risk groups such as immunocompromised individuals, pregnant women or the elderly. The risk arboviruses pose to blood safety was first demonstrated for West Nile virus (WNV) following its emergence in the United States of America (USA) in 20023. Transfusion transmitted infections have since been observed for dengue (DENV) and Zika viruses (ZIKV)4,5. Different blood components have been associated with transfusion-transmitted infections including platelets, red blood cells and plasma for WNV and DENV, and platelets for ZIKV6.
How are blood services globally managing current and future arboviral risks?
The Virology Subgroup of the ISBT TTID WP conducted an international survey to better understand how blood establishments currently manage arboviral risks and how prepared they are for the emergence of new threats. The survey focused on six arboviruses of concern: WNV, DENV, ZIKV, chikungunya virus (CHIKV), Japanese encephalitis virus (JEV) and Usutu virus (USUV). The survey was distributed through the ISBT TTID WP and collected data from 2024. Twenty-three blood establishments responded to our survey, including national and regional services collectively representing almost 1.5 billion people and approximately 30 million blood donations. This work has been recently published, and contains further participant details, survey questions and results7.
Measures used by blood services against arboviral risks
The survey demonstrated considerable variation in the mitigation strategies to prevent transfusion-associated arbovirus transmission, which included donor deferrals based on travel history or local epidemiology, pathogen reduction, and nucleic acid amplification testing (NAT). Where NAT for arboviruses is performed, it is primarily directed at WNV and conducted by blood services in North America and Europe (Figure 1).
Testing strategies included individual-donation (ID) NAT and various forms of pooled NAT, with pool sizes varying considerably between blood operators. Some blood operators indicated they switched from pooled NAT to ID-NAT during the WNV transmission season or following the identification of a WNV infection in areas surrounding where a donor lives for 7 days after detection. Confirmatory testing for WNV reactive samples also varied, including repeat testing of the original sample, testing of a second sample from the same donation and the use of different assays or sequencing approaches. There were 394 initially WNV-reactive samples of which 256 donations (65%) were confirmed as WNV RNA-positive in 2024 (2.9 per 100,000 screened). Confirmatory testing has an important role in blood transfusion safety. As many arboviruses co-circulate, potential cross-reactivity in screening assays makes identifying the causative virus an issue. Establishing standardised approaches for RT- PCR and sequencing could help resolve initially reactive results and provide information on circulating viral strains in the donor population, improving both blood safety and epidemiological surveillance.
Meanwhile, despite the increasing international concern surrounding viruses such as DENV, CHIKV and ZIKV, routine screening for these infections was not reported by the participating blood establishments. Several blood operators nevertheless indicated that they had the capacity to introduce additional screening if a local outbreak occurred or circumstances justified such an intervention. The survey also demonstrated the importance of donor deferral based on travel history. Almost 80% of responding blood establishments reported deferring donors following travel to areas where relevant arboviruses are endemic. Deferral periods varied, with approximately 28 days being the most frequently reported duration. This strategy is particularly useful where local transmission is absent or limited but becomes more difficult when sustained local transmission occurs.
Pathogen reduction was reported by 52% of respondents, although its use was limited to platelets and plasma. Use was higher among respondents from high-income countries than among those from upper-middle-income countries (65% vs. 25%). Pathogen reduction may be most valuable in countries with greater arbovirus endemicity, although wider implementation will depend on factors including cost and applicability across blood components8.
Figure 1. WNV NAT screening practices of participating blood services in the survey. Red shading indicates the blood establishments that screen for WNV using NAT, and grey shading shows the establishments that do not screen for WNV.
Main findings and implications
These findings highlight an important distinction between preparedness and current routine testing. Blood establishments may not need to screen universally for every emerging arbovirus, but they should have mechanisms capable of detecting changes in epidemiology and triggering an appropriate response. The survey therefore raises questions about what signals should prompt a transition from donor questioning and deferral to laboratory screening. Examples of such triggers could include the detection of a positive donation or an increase in locally reported cases. The survey’s findings reinforce the importance of preparedness in a changing epidemiological environment. Climate change and global mobility may alter the geographical distribution of vectors and viruses, but the effects will not necessarily be uniform. Blood services therefore need flexible, evidence-based strategies that incorporate local epidemiology, one health surveillance information and the capacity to activate additional interventions when necessary. The study provides an important international snapshot of current practice while identifying several areas for future collaboration. Rather than asking whether every emerging arbovirus should be screened routinely, the central question is how blood establishments can recognise early signals, assess risk and respond rapidly enough to protect the blood supply.
References
1. Lim A, Shearer FM, Sewalk K, Pigott DM, Clarke J, Ghouse A, et al. The overlapping global distribution of dengue, chikungunya, Zika and yellow fever. Nature communications. 2025;16(1):3418. 2. Giménez-Richarte Á, Ortiz de Salazar MI, Giménez-Richarte M-P, Collado M, Fernández PL, Clavijo C, et al. Transfusion-transmitted arboviruses: Update and systematic review. PLoS neglected tropical diseases. 2022;16(10):e0010843. 3. Pealer LN, Marfin AA, Petersen LR, Lanciotti RS, Page PL, Stramer SL, et al. Transmission of West Nile virus through blood transfusion in the United States in 2002. New England Journal of Medicine. 2003;349(13):1236-45. 4. Perera L, De Zoysa N, Jayarajah U, Senanayake N, De Zoysa I, Seneviratne SL. Transfusion-transmissible dengue infections. Transactions of the Royal Society of Tropical Medicine and Hygiene. 2020;114(11):866-82. 5. Motta IJ, Spencer BR, Cordeiro da Silva SG, Arruda MB, Dobbin JA, Gonzaga YB, et al. Evidence for transmission of Zika virus by platelet transfusion. New England Journal of Medicine. 2016;375(11):1101–1103.
6. ECDC. European Centre for Disease Prevention and Control. Transmission of selected arboviruses through substances of human origin (SoHO) - A scoping review. Stockholm; 2026. 7. Rajendra P, Faddy HM, Candotti D, Bub CB, Kutner JM, Drews SJ, et al. An international study on emerging arboviral infections and blood safety. 2026 Sep;66(9):1786-1799. doi: 10.1111/trf.70306. 8. Rebulla P. The long and winding road to pathogen reduction of platelets, red blood cells and whole blood. British Journal of Haematology. 2019;186(5):655-67.
