To further support a WNV diagnosis, we performed immunohistochemical staining on brain tissue. The immunoperoxidase stain used was a commercial rabbit polyclonal antibody (BioRelience Corp., Rockville, MD, USA) with peroxidase-tagged goat antirabbit immunoglobulin G (DakoCytomation, Carpinteria, CA, USA) bridge and 3-amino-9-ethylcarbazole (DakoCytomation) as the chromogen. This staining demonstrated abundant WNV antigen within the cytoplasm of a small number of neurons and glial cells and in fewer macrophages in the brain tissue (Figure) .