West Nile Virus Infection in the Immunocompromised Patient.

West Nile virus infection has become the predominant cause of flavivirus-associated encephalitis in the US. While 80 % of infected individuals are asymptomatic, 20 % develop symptoms including fever, headache, transient rash and gastrointestinal symptoms. Among the immunocompetent population, 1 in 150 develop neuroinvasive disease characterized by acute flaccid paralysis, Parkinsonian cogwheel rigidity, meningitis, encephalitis, meningoencephalitis and asymmetric muscle weakness (Mostashari et al. in Lancet 358:261-264, 2001). In the immunocompromised population such as transplant recipients and HIV-infected and chemotherapy patients, the incidence of neuroinvasive disease may be increased. The largest population studied is recipients of solid organ transplants, with data on both donor-derived and naturally occurring transmissions. The risk of neuroinvasive disease in donor-derived infection is estimated to be between 50 % and 75 % while in those with mosquito-borne transmission the risk is estimated at 40 % of those infected (Kumar et al. in Am J Transplant 4:1883-1888, 2004). With significant morbidity associated with donor transmission, specific pretransplant screening recommendations are reviewed. Treatment includes supportive care and consideration for the use of intravenous immunoglobulin.