Evidence of West Nile virus exposure in healthy donors and a clinical case in an immunocompromised child: emerging public health implications

Background West Nile virus (WNV), an emerging mosquito-borne flavivirus, is a growing global concern, particularly in tropical regions, where climatic conditions favor vector proliferation. Although often asymptomatic, less than 1% of cases develop severe neuroinvasive disease, primarily among the elderly or immunocompromised. Transfusion-transmitted WNV infections have been documented but remain underrecognized in the Middle East. Methods This study reports a case of a 4-year-old Saudi girl with Ewing’s sarcoma undergoing chemotherapy who developed WNV encephalitis following multiple blood transfusions from 30 healthy blood donors. The investigation was conducted at a tertiary hospital in Jeddah. Serological screening of 30 blood donors was performed to identify potential sources of infection. Results The patient presented with febrile seizures, and MRI findings of bilateral thalamic and midbrain signal changes were consistent with viral encephalitis. WNV infection in the patient was confirmed by the polymerase chain reaction. The clinical picture correlated with reported cases of transfusion-associated WNV infection in immunocompromised hosts. Four of the 30 donor samples (13.3%) tested positive for anti-WNV antibodies, indicating prior exposure among donors and supporting transfusion as a plausible but unconfirmed transmission route, as retrospective molecular testing of implicated blood units was not available. Conclusion This case underscores the need to consider the incorporation of nucleic acid testing (NAT) for WNV RNA into pretransfusion screening protocols, particularly for high-risk recipients and during peak transmission periods, to reduce the risk of transfusion-transmitted infection. The detection of anti-WNV antibodies among healthy donors highlights the silent viral circulation in the community. Strengthening national surveillance systems, enhancing vector control measures, and improving clinician awareness are vital to mitigate transfusion-related WNV transmission in endemic and emerging regions.