Persistent signs and symptoms of vague viral illness with elevated WNV IgM and IgG.

I am an Internist in Thornton, Colorado following a 45 years-old HispanicAmerican male who developed fever, headaches, muscle aches, excessive fatigue and a skin rash on his face in August 2006. His West Nile Virus IgM has been positive persistently (6.21 in August 2006; 2.09 in September 2007; 1.58 in September 2008; and 1.76 on 05/18/2009. The corresponding IgG for WNV has also remained elevated.

My 2 questions are as follows:

1. Does persistent elevation of WNV IgM along with WNV IgG mean a "chronic active" infection with the virus - especially since the patient continue to show symptoms and signs?

2. Is there a "quantative cut-off" level of WNV IgM for suggesting that diagnosis?