Background.

West Nile virus (WNV) is rapidly spreading through North America. In the general population, the majority of WNV infections are asymptomatic. During 2002, an outbreak of WNV occurred in Toronto, Canada. We observed four cases of severe symptomatic community-acquired WNV infection in our organ-transplant population.

Methods.

Patient data were obtained from chart review. WNV was diagnosed by acute and convalescent serology. Incidence was compared with data obtained from a population-based surveillance program.

Results.

Four transplant patients had WNV encephalitis (n= 3) or meningitis (n= 1). Mean age was 44.5 (range 26–58) years and transplant type included kidney (n= 2), liver (n= 1), and heart (n= 1). The mean time posttransplant was 3.8 years (range 2 months–8 years). The presenting symptoms were fever (4/4), confusion (3/4), headache (4/4), and weakness (2/4). Cerebrospinal fluid showed a pleocytosis in all patients and elevated protein in three of four. All patients had identifiable occupational or recreational risk factors. There was no evidence that the infection was acquired by transfusion or the transplanted organ. Outcomes were full recovery (2/4), lower limb paralysis (1/4), and death (1/4). On the basis of active population surveillance data, the rate of WNV meningoencephalitis in the general population in the Toronto area was approximately 5 per 100,000. This compares to four cases in a transplant population of 2,000 patients (rate 200 per 100,000)(P< 0.001).

Conclusions.

Transplant patients are likely at greater risk of severe neurologic disease caused by community-acquired WNV compared with the general population. Prevention of transmission and patient education may be more important in this population.