A probable case of West Nile virus transfusion transmission

BACKGROUNDTransfusion-transmitted West Nile virus (WNV) infection is infrequent as a result of minipool (MP) and individual-donation (ID) nucleic acid testing (NAT) of blood donations. ID-NAT is triggered on the basis of local WNV activity identified by MP-NAT. STUDY DESIGN AND METHODSA 78-year-old male patient who was treated for cardiac disease received 14 blood components from 30 donors in August 2016. He was discharged 7 days after aortic valve replacement and coronary bypass surgery, but was re-admitted on Day 12 with symptoms of viral infection, and eventually was diagnosed with aseptic meningitis. The patent died on Day 51. RESULTSThe patient was positive for WNV-immunoglobulin M (IgM) antibodies in his cerebrospinal fluid on Day 14 and was positive for WNV-IgM (on Days 14 and 16) and WNV-IgG antibodies (on Day 16) in his serum. All associated donations were nonreactive by MP-NAT or ID-NAT. However, one MP-NAT was noted to have an elevated (but negative) signal-to-cutoff ratio, and one donor from that MP was subsequently found positive for WNV-IgM and IgG antibodies; the donor was diagnosed with a WNV-like viral syndrome that had an onset 3 to 5 days postdonation. The donor's plasma was transfused 12 days before the patient's onset of WNV-meningoencephalitis. Conversion to ID-NAT was triggered for the region 7 days after the implicated donation, which was associated with the region's first human WNV case. CONCLUSIONDespite the possibility of mosquito-borne transmission, this was considered to be a case of transfusion-transmitted WNV infection from an MP-NAT-nonreactive donation collected just before triggering conversion to ID-NAT; a rare event recognized once in 84 million donations.