I have mentioned this in another post but thought it was worth a post of its own. From what i have read viral titres may not be that important but go hand in hand with symptoms as healthy people can have high viral titres to igm and igg and no symptoms or active infections. This link refers to cmv but would think it also refers to other herpes viruses. Whats interesting is that it mentions immunocompromised patients can have active infections going on but have lower igm and igg then expected. cfs/me are immunocompromised people. Maybe nk function testing with symptoms, possibly cd8 t-cells and viral testing is the best way to tell if you have an active infection. What does the test result mean? Care must be taken when interpreting the results of CMV testing. The doctor evaluates the results in conjunction with clinical findings, including signs and symptoms. It can sometimes be difficult to distinguish between a latent, active or reactivated CMV infection. This is due to several reasons, including: A healthy person who has been infected with CMV at one time will continue to harbor the virus. The CMV can reactivate intermittently, often sub-clinically, shedding small amounts of virus into body fluids but not causing symptoms. An immune-compromised person may not have a strong antibody response to the CMV infection their IgM and IgG levels may be lower than expected even though they have an active case of CMV. The virus may not be present in sufficient number in the particular fluid or tissue tested to able to be detected. http://labtestsonline.org/understanding/analytes/cmv/tab/test cheers!!!