--what makes your doctor think this is West Nile? Have you been titred up for the antibodies by ELISA test, and, if this was positive, has it been confirmed by Western Blot test?

Wings has a point about watching for the "bird signs", as does Dahlek--the testing for both West Nile and Lyme can be rather unreliable.

There are certainly numerous other infections that could be causing your symptoms--not to mention this could be well within the pararmeters of an IVIg reaction (and yes, IVIg is most certainly a blood product)--how extensive/exhaustive has the testing for this been?