I can give you my opinion. It appears I need IVIG about every 6 to 8 weeks. I can feel myself getting weaker as that time approaches. Thus far I have taken Imuran, CellCept, steroids, and Mestinon but none of those seen to help.

As for viruses and getting sick that happened to me about three weeks ago. At that point in time I was doing fairly well but was getting due for my IVIG treatment, at that point I got an infection or virus for two days. My general practitioner put me on antibiotics and it cleared right up. When the virus cleared up I became very weak maybe the weakest that I have been. I am currently getting IVIG treatments and have had three so far with no results. My Neuro called an increased my Mestinon to 90 mg four times a day. No results from that either. On two day notice he scheduled me for an immediate appointment. This setback has caused new problems, I have new issues with my eyes they both periodically want to close, overall general weakness is worse, cramps are worse in my legs and feet and my shaking has increased. So in my opinion getting sick with a virus or infection can really set you back.
I will try to remember to reply tomorrow after my Dr appt.
Mike