One to five percent of college students develop infectious mononucleosis each year, and about 10 percent are diagnosed six months later with chronic fatigue syndrome -- a complex condition involving severe fatigue coupled with disabling cognitive and musculoskeletal symptoms. To assess risk factors for chronic fatigue syndrome after mononucleosis, researchers developed and validated a scale for rating the severity of mononucleosis. In a study with 126 college students, they found that participants with a higher mononucleosis severity score had over three times the risk of meeting two or more sets of diagnostic criteria for chronic fatigue syndrome after six months, as well as almost twice the chance of being prescribed steroids and an increased risk of being hospitalized during the acute illness. Their findings were published in the Journal of Pediatrics."Our simple and objective assessment tool allows clinicians to identify patients at risk for more serious infectious mononucleosis, including those who might develop chronic fatigue syndrome following infectious mononucleosis," says lead author Ben Katz, MD, specialist in pediatric infectious diseases at Ann & Robert H. Lurie Children's Hospital of Chicago and Professor of Pediatrics at Northwestern University Feinberg School of Medicine. "This allows an opportunity to potentially intervene early in efforts to prevent chronic fatigue syndrome that develops in this setting."

Chronic fatigue syndrome has a profound impact on an individual's ability to function, and it may take a long time recover. Previous research by Dr. Katz and colleagues, published in Pediatrics, showed that adolescents who developed chronic fatigue syndrome after mononucleosis gradually got better, although 4 percent were still suffering from the condition two years later.

Although chronic fatigue syndrome tends to follow infectious mononucleosis in some people, no evidence of a lingering virus is detected. "It appears that chronic fatigue syndrome might involve a combination of immunologic and psychologic factors, but we still don't know the exact cause or causes," says Dr. Katz.

Multiple studies have identified two treatments that may be effective for chronic fatigue syndrome -- graded exercise therapy (physical activity that starts out slowly and is gradually increased over time) and cognitive behavioral therapy.

"Potential follow-up research will evaluate if treatment for chronic fatigue syndrome begun at the time severe mononucleosis is diagnosed can reduce the chances of developing this challenging condition six months later," says Dr. Katz.