• Safety (including all causes of mortality) in the test IVIg (Omr-IgG-am™) group versus the 2 placebo groups, as defined by the total number of serious adverse events regardless of relatedness to study drug administration. [ Time Frame: Duration of study. ] [ Designated as safety issue: Yes ]
  

• Pharmacokinetics of specific anti-WNV antibodies as measured by ELISA and PRNT methods. [ Time Frame: Baseline (pre-dose) blood sample collected immediately prior to the beginning of the infusion. After the infusion, additional blood samples collected at 1 hr, 6 hr, 12 hr, 24 hr, 72 hr, and then at Day 5, Day 7, Day 14, Day 30, Day 60 and Day 90. ] [ Designated as safety issue: No ]
  
• Mortality alone among confirmed WNV patients. [ Time Frame: At 3 months. ] [ Designated as safety issue: No ]
  
• Combined primary endpoint of mortality and morbidity among confirmed WNV patients as assessed by four scoring systems: the Barthel Index, the MRS, the GOS and the 3MS, in the experimental treatment group versus the control group. [ Time Frame: At 3 months. ] [ Designated as safety issue: No ]
  
• Combined morbidity and mortality in treatment versus placebo groups for all (including those without WNV infection) subjects by intention to treat analysis. [ Time Frame: At 3 months. ] [ Designated as safety issue: No ]
  
• Proportion of patients returning to pre-morbid baseline at 3 months, between treated and untreated groups of patients with WNV infection, as assessed by two scoring systems the Barthel Index and the MRS. [ Time Frame: At 3 months. ] [ Designated as safety issue: No ]
  
• Improvement as compared to subject's own worst (of any earlier) evaluation, for each subject as defined by the combined results of the 4 neurological functional tests. [ Time Frame: At 3 months. ] [ Designated as safety issue: No ]
  

The purpose of this study is to assess whether Omr-IgG-am™, an intravenous immunoglobulin (IVIg) containing antibodies specific for West Nile virus (WNV), is safe and well-tolerated in patients with suspected or laboratory diagnosed WNV disease. An initial estimation of efficacy will also be made. This Phase I/II study will enroll hospitalized adults with a presumptive diagnosis of West Nile encephalitis and/or myelitis or those with a positive laboratory test for diagnosis of WNV infection who are at high risk for progressing to severe neurologic disease based on age or immunosuppression. Patients will be randomized in blocks of five to receive either Omr-IgGam ™, Polygam® S/D (IVIG containing minimal anti-WNV antibodies) or normal saline in a ratio of 3:1:1. Patients and investigators will be blinded to treatment assignments. Patients will receive a single intravenous dose of study medication or one of two placebos. The study participants will receive 0.5 grams/kg of Omr-IgG-am™ or Polygam® S/D or a comparable volume of normal saline. All patients will be followed for safety, natural history endpoints, and efficacy. A subset of patients will have pharmacokinetic measurements of specific anti-WNV antibodies assessed following treatment. The primary endpoints are safety and tolerability following Omr-IgG-am™ administration. Secondary endpoints include pharmacokinetics of specific anti-WNV antibodies, mortality in confirmed WNV positive patients, and the combination of mortality and functional status at three months in both confirmed WNV-infected patients and all patients by intention to treat. This combined endpoint will be measured using four standardized measures of cognitive and functional status: the Barthel Index; the Modified Rankin Scale; the Glasgow Outcome Score; and the Modified Mini-Mental Status Examination. A comparison of outcomes will be made for the group receiving Omr-IgG-am™ versus those receiving either placebo, and between the two placebo groups. Other secondary endpoints include the proportion of patients in each group returning to pre-morbid baseline and each subject's improvement at 3 months as compared to that subject's worst (of any previous) evaluation. Natural history endpoints will also be assessed. They will include the duration of intensive care unit and hospital stay, development and persistence of WNV-specific IgG and IgM antibodies, combined functional score and mortality at 3 months between the group with encephalitis and/or myelitis at baseline versus the group with a positive WNV test only, outcomes in patients treated late in coma and correlation of outcome with time-to-treatment following symptom onset.