Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Chronic Fatigue Syndrome Health Center

Font Size

Virus Linked to Chronic Fatigue Syndrome

Study Shows MLV Is in Blood of People With Chronic Fatigue Syndrome
WebMD Health News
Reviewed by Laura J. Martin, MD

Aug. 23, 2010 -- Murine leukemia viruses (MLV), a family of retroviruses known to cause cancer in mice, may be linked to chronic fatigue syndrome (CFS), a study shows.

The full name of the virus is xenotropic murine leukemia virus-related virus. It is part of a family of viruses known as murine leukemia viruses (MLV), which is a type of retrovirus known to cause cancer in mice.

The new study, published in the Proceedings of the National Academy of Sciences, conflicts with some earlier studies. Several U.S. studies, including a recent report from the CDC and research done in the U.K. and the Netherlands, found no evidence of MLV in the blood of people with CFS. One recent study, however, found evidence of an MLV-related virus called XMRV in blood cells of patients with CFS.

The new study shows that 86.5% of 37 people with CFS had evidence of murine leukemia virus in their blood, as did 6.8% healthy blood donors.

"There is a dramatic association with CFS, [but] we have not determined causality for this agent," said Harvey Alter, MD, chief of clinical studies and associate director for research in the department of transfusion medicine at the National Institutes of Health (NIH) Clinical Center in Bethesda, Md., at a news conference. "Other labs have not found this virus, so a dilemma at present is how to reconcile that some labs find the association and others do not."

"We think it is in the patient populations, not the lab testing [contamination causing a false-positive lab result], but the latter has not been completely ruled out," he says.

More Questions Than Answers?

Steve Monroe, PhD, director of the division of high-consequence pathogens and pathology at the CDC, tells WebMD that the new study "raises as many questions as it answers and there are still a lot of things about this virus that we don't know."

Andrew L. Mason, an associate professor of medicine at the University of Alberta in Edmonton, Alberta, Canada, says it's time to act, not point fingers.

There have been several studies showing the presence of this virus in the blood of people with chronic fatigue syndrome and prostate cancer, but other studies have not found it.

Today on WebMD

8 Symptoms Of Chronic Fatigue Syndrome
Always Sleepy Causes Fixes For Fat
Insomnia 20 Tips For Better Sleep
Exercises That Can Increase Your Energy
10 Ways To Get More Zip In Your Life
Fatigue or Something More
Your Symptoms
young woman hiding face