OROV RNA Detected in Blood Donors During 2023–24 Brazil Outbreak

Nucleic acid testing (NAT) surveillance of blood donors in Brazil’s Amazonas state found that 6.5% of donor minipools tested positive for Oropouche virus (OROV) RNA during the country’s widespread 2023–24 outbreak, indicating that asymptomatic, viremic donations may have been present in the blood supply during peak transmission. The findings were published recently in The Journal of Infectious Diseases.

Donor Surveillance and Viral Detection

As part of the study, investigators from the Vitalant Research Institute and Fundação Hospitalar de Hematologia e Hemoterapia do Amazonas (HEMOAM) used a validated RT-qPCR assay to test 661 minipools collected between November 2023 and May 2024, representing approximately 11,900 donations.

Peak minipool reactivity reached 39% in January 2024, coinciding with peak reported cases in Amazonas state. This corresponded to an estimated donor-level NAT positivity of approximately 2.69% during the peak month, derived using standard pooled-testing models, although investigators noted this may be underestimated due to reduced analytical sensitivity inherent to minipool testing.

Among 43 OROV-reactive pools, 22 contained viral loads above the assay’s limit of quantification, while the remaining 21 had detectable but non-quantifiable RNA levels. According to investigators, this suggests that some asymptomatic donors exhibited viremia comparable to that observed in symptomatic infections.

Using a prevalence–incidence framework integrating NAT yield with seroincidence, investigators estimated an RNA-detectable window of approximately 5.4 days, consistent with estimates for other arboviruses evaluated using minipool NAT. Serologic data showed donor seropositivity increased from 13% before the outbreak to 29.7% afterward, suggesting that the true infection burden may be higher than reported case counts.

Implications for Blood Safety

Although transfusion-transmitted OROV infection has not been reported, these findings support biologic plausibility for transfusion transmission during periods of elevated community incidence. However, investigators emphasized that detection of viral RNA alone does not establish infectivity or clinical transmission risk. They emphasized that further evaluation, including individual donation NAT, donor–recipient linkage studies and infectivity studies using animal models, are necessary to define transfusion risk and inform potential blood safety interventions.

Additional information about OROV and potential implications for transfusion safety is available in AABB’s emerging infectious diseases fact sheets.