A patient with leg weakness.

The present case was typical in many respects for neuroinvasive WNV infection. The differential diagnosis considered was appropriately comprehensive. The present case also reminds us that little or no abnormalities will be seen on imaging in many cases, and that initial serology may be negative and should be repeated beyond the acute phase ante- or postmortem. Fortunately, specific antibodies are also now available for identification of viral proteins in tissue although sensitivity of the latter may be affected by the stage of infection and sampling of areas bearing a higher viral load. West Nile Virus, along with other emerging infections, serves notice of the health care implications of humanity's globalization of ecosystems.