On April 26, 2013, the United Network for Organ Sharing reported to CDC a cluster of ill organ transplant recipients in Iowa with a common organ donor. Infection with lymphocytic choriomeningitis virus (LCMV) was suspected. LCMV is a rodent-borne virus that most commonly causes nonfatal, influenza-like illness and occasional aseptic meningitis, but when transmitted through organ transplantation or in utero can cause severe, life-threatening disease.