Chronic Fatigue May Have a Viral Link

New research links chronic fatigue syndrome to a virus that lives in the gut.

December 10, 2008, 5:34 PM

Sept. 13, 2007 — -- Feeling tired? There's a chance that lethargic feeling may have less to do with a hectic schedule and more to do with a stomach virus.

In a study published Wednesday in the Journal of Clinical Pathology, researchers in California suggest that chronic fatigue syndrome may be linked to the presence of enteroviruses -- viral microorganisms that reside in the digestive tract.

More than 1 million people are believed to suffer from CFS, a debilitating disease without any known cause or cure. The condition is associated with persistent fatigue that severely limits day-to-day activities.

And many patients with CFS also complain of stomach pain and indigestion -- a correlation that led study author Dr. John Chia and co-investigator Andrew Chia of Enterovirus Medical Research to investigate further.

What they discovered by analyzing samples of stomach tissue from 165 patients with CFS was that 82 percent of these individuals had high levels of enteroviruses in their digestive systems.

"I believe that chronic antiviral infections are an important cause of CFS," said lead author Chia. "This finding will open the door to research on how the viruses work in the body and how antiviral drugs can be developed to treat these symptoms."

Other experts in the field shared Chia's optimism. Dr. Nancy Klimas, a professor of medicine at the University of Miami School of Medicine said the research may have revealed a link that nobody expected.

"It's a very powerful study, and one that is hard to dismiss because he looked at so many patients," she said. "I think he is on to something very important here."

In recent years, microorganisms in the gut have been fingered as culprits in other maladies -- the most notable example being the link established between the stomach bacteria Helicobacter pylori and stomach ulcers, which netted Australian scientists Barry Marshall and Robin Warren a Nobel Prize in 2005.

The stomach virus, Chia believes, that is linked to CFS enters the body through the gastrointestinal tract and then moves on to infect other tissues, such as the central nervous system and the heart. It begins as an acute infection, causing flulike symptoms and stomachaches. But then it lingers -- and in some people, it develops into a chronic infection that causes CFS.

Unlike traditional viruses that infect and kill cells, the enterovirus "has adapted to grow inside of a cell but does not kill it," said Chia. The cell protects the virus and allows it to thrive. So although the body's immune system tries to fight off the virus, it does not succeed.

But the immune system does not give up. Rather, it continues to try to fight the virus -- a process that stresses the body, causing fatigue and stomach pain.

This most recent study is not the first one to identify a virus as the possible cause of CFS. When research on CFS began about 20 years ago, scientists believed viruses to be the culprit. At this time, unfortunately, researchers were either looking at the wrong types of viruses or didn't have the technology to find the right ones.

"When scientists couldn't prove that CFS was linked to viruses, they moved on," said Klimas. "In the next seven to eight years, research was heavily focused on hormones and the autonomic nervous system. However, with the human genome project and all the advances in genetics, there are now new tools available to look for viruses."

One reason that the virus Chia has implicated in CFS may have been so hard to pin down is the fact that it does not appear in the blood. In light of this, Chia looked for the viral proteins in the stomach tissue itself.

"We looked for the viral proteins in stomach cells of patients with CFS and of patients without CFS, who served as controls," Chia said. "We found tons of patients with CFS who had the viral proteins."

And although about 20 percent of the control patients also tested positive for the virus, they had only a small amount of it in their tissue. In contrast, the stomach cells of patients with CFS were swarming with it.

Many researchers believe that enteroviruses are not the only cause of CFS.

"There are over 15 different pathogens contributing to CFS," said Kristin Loomis, president and executive director of the HHV-6 Foundation, which funds viral research. "Enteroviruses are one, HHV-6 is another, and Epstein-Barr virus is a third."

With so many different viruses, it may seem impossible to tackle the disease. However, certain antiviral drugs have already been developed that target specific viruses and can be used to treat certain groups of CFS patients.

In one example, doctors at Stanford University School of Medicine are using the antiviral drug valganciclovir to treat CFS -- with promising results so far.

And Chia believes that as long as other scientists in the field confirm his results, drugs to fight enteroviruses will be available within five years.

"However," Klimas warned, "there are not antiviral drugs to cover all viruses. … I think we should look at treatments that make the immune system stronger and less susceptible to viral infection."

There is hope for CFS patients, Chia believes, even if it comes 20 years too late.

"I think it's a good year for CFS," he said. "Federal agencies have recognized the severity of the disease. It has been brought to the public's attention by the media, and now it's the drug companies' turn to start developing antiviral medications."

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