Encephalitis from west nile virus. what is death rate/cute rate? what treatments are available

Hard to say: Some studies have quoted mortality from neuroinvasive cases of wnv ~5%, but this must be a huge overestimate. Maybe 3 in 1000 of all cases are severe (or neuroinvasive), so you might guess less than 1 in 5000 cases die. Most of the deaths appear to come in the elderly, chronically ill or immunosuppressed. Treatment is mainly supportive (including intubation & ventilation in severe cases).

West Nile virus: In patients with WNV encephalitis, the overall mortality is approximately 12–15%, although it could be as high as 35% in elderly patients. REF: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3773989/ Treatment is supportive.