The answer to that is: Yes. No. Maybe.
32 of 37 (86.5%) compared with only 3 of 44 (6.8%) healthy volunteer blood donors.
This confirms a study published in Science that a class of retroviruses (MLV-related viruses) may be involved in the disease. The take-home message from these two studies is that researchers found traces of this virus in the majority of patients studied, and very rarely in healthy controls.
However, other studies conducted in the UK and the Netherlands, found no correlation between CFS patients and MLV-related viral infections. And more confusingly, a study posted in the Journal of Retrovirology by the CDC in July stated that there was no correlation in patients from the US .
So what does this all mean? Well, at this point, it means we don’t know why there is conflicting data. The PNAS paper does a nice job of detailing what the problems may be. There may have been a problem in the CDC study in that the patients were not properly diagnosed with CFS (some individuals tested may have had depression or another infection that can mimic some symptoms of CFS). There may be some geographic restrictions as to where the virally associated CFS is occurring. Finally, the differences in the way the testing was conducted in each study may have played a large role in the difference of outcomes (most were PCR studies and different primers have different detection capabilities). Scientists are now working out more uniform experimental procedures and guidelines for testing whether or not there is a real CFS association with MLV-related viruses.
There is a strong enough link that blood banks are discouraging CFS patients from donating blood as a precaution just in case the disease may indeed be due to an infectious agent.
But there may be real hope on the horizon for understanding, treating and limiting the spread of this disease.