High titer human immunoglobulin as a specific therapy against West Nile virus encephalitis.

West Nile virus (WNV) is a mosquito-borne disease found most commonly in Africa, west Asia, and the Middle East, where up to 40% of the human population possesses antibodies. It is an emerging disease in the United States, since 1999 and has spread all over the US and Canada. The virus is maintained in nature in a mosquito-bird-mosquito cycle (primarily Culex), with human horses and other animals serving as incidental hosts. WN infection in humans is usually asymptomatic or involves flu like illness but can develop to severe meningo-encephlitis, with symptoms including cognitive dysfunctions, muscle weakness, paralysis and even death. Elderly and depressed immunity factors are at greatest risk of developing severe neurological disease. Studies in animal models have enhanced significantly the understanding of the viral and host factors that determine the pathogenesis and outcome of WNV disease. Currently, vaccines are available for animal use but there is no effective antiviral therapy or human vaccine for WNV infection. Passive administration of antibodies produced from selected donors has shown promising results in animal models.