Researchers Identify Asymptomatic WEEV Infection in Argentine Blood Donor

Researchers in Argentina detected an asymptomatic, viremic blood donor during the country’s 2023-24 outbreak of western equine encephalitis virus (WEEV). The findings were published in Emerging Infectious Diseases.

The Emerging Infectious Diseases (EID) group of AABB’s Transfusion Transmitted Diseases Committee reviewed the manuscript and found the observation both expected and consistent with findings reported during outbreaks of WEEV and other arboviral disease agents like West Nile virus, dengue virus, St. Louis encephalitis and others.

WEEV reemerged in Argentina in 2023 after nearly three decades. Prior to this, the last confirmed human case occurred in 1996. During the outbreak, health authorities confirmed 107 human cases and 12 deaths. There are no screening tests or specific donor deferral criteria for WEEV.

To evaluate the potential effect of WEEV circulation on transfusion safety, the Fundación Banco Central de Sangre implemented a hemovigilance response tailored to the regional outbreak. The strategy combined real-time epidemiologic mapping, community-informed donor screening questions, reinforced postdonation symptom reporting and retrospective alphavirus-specific nucleic acid testing (NAT) of plasma from donors in affected areas.

Among 4,048 donors who gave blood during the intervention period, 637 lived in areas mapped as having suspected WEEV circulation. NAT of samples from those donors identified a single viremic donor whose viral sequence clustered within the contemporary South American outbreak lineage.

The authors described blood donors as a sentinel population for detecting silent viral circulation that symptom-based surveillance may miss and called for integrating molecular surveillance into routine blood bank practices.