BACKGROUND & PURPOSE: The incidence of West Nile Virus (WNV) in the US has increased dramatically since 1999. By 2003 WNV was found in virtually all regions of the US. A small percentage (1/150, or < 1%) of patients with WNV develop West Nile Neuroinvasive Disease (WNND) with encephalitis and flaccid paralysis. Evidence-based practice (EBP) is difficult to use with an emerging disease since there is a relative absence of literature to critique. The purpose of this case report is to describe the PT care and outcomes of a patient with WNND and the therapist's efforts to employ an EBP approach with this emerging disease. CASE DESCRIPTION: The patient was a healthy, physically active 55 year old female physician assistant who became acutely ill several days after traveling from her home in Colorado to France in August, 2003. Following a 12 day hospitalization in France, she was transferred to a hospital in Colorado. In this setting the patient presented with asymmetrical lower extremity weakness with the left side (2 to 3/5) more involved than the right (3 to 4/5). The therapist determined there was no research literature directly related to the PT care of patients with WNND. She then consulted local and national medical and physical therapy experts. From these communications she learned that a small number of patients with WNND who received little or no PT had poor functional recovery. The therapist conferred with the patient, then elected to use a post-polio ‘period of recovery’ approach using intensive strengthening and careful monitoring of fatigue. OUTCOMES: The patient began her rehabilitation during week 3 post-onset (PO) and at that time was able ambulate with a front-wheeled walker. She progressed to a wide based quad cane and driving at week 12; a single point cane at week 13, and began some ambulation without an assistive device by week 20, at which time the patient returned to work part-time. By week 43 PO the patient had returned to work full time, and at week 49 was able to ambulate in the community without an assistive device. At week 50 the patient was able to hike up to 5 miles using bilateral trekking poles. DISCUSSION: The progress of this patient may not be typical of other patients with WNND. She was relatively young and extremely fit prior to the onset of the illness, and also very motivated and adherent to her rehabilitation program. The outcomes described in this case, combined with the poor outcomes of the patients with WNND who received little or no physical therapy, suggest the value of appropriately graded, but intensive approach to strengthening and rehabilitation, moderated by regular assessment of fatigue. The long term consequences of this approach are not known. The use of an EBP approach to the PT care of a patient with an emerging disease (when the literature is inadequate or absent) must shift from a critical review of research literature to consulting with experts, and integrating this information with input from the patient and the therapist's experience.