Because some cases of chronic fatigue and immune dysfunction syndrome (CFIDS) begin with a flu-like infection, several viruses have been studied as possible causes of CFIDS.¹ None have been found to be the cause of CFIDS because all are relatively common in the general population and researchers have been unable to link any of them to all cases of CFIDS.

There is still much debate in scientific circles over whether any infectious agent will emerge as the only cause of CFIDS. Current thinking is that there may ultimately be found several triggers for the illness in genetically, environmentally or otherwise susceptible individuals.²

Epstein-Barr Virus
In the mid-1980s, several researchers reported slightly higher levels of antibodies to Epstein-Barr virus (EBV) in patients with CFIDS-like symptoms compared with healthy individuals.^3,4 Most of these patients had experienced an episode of infectious mononucleosis a few years before the onset of chronically fatiguing symptoms. As a result, the illness became known as "chronic Epstein-Barr syndrome."

In subsequent investigations, it became clear that elevated EBV antibody titers are not diagnostic for CFIDS⁵; some healthy people have high titers of EBV, and some people with CFIDS do not. More than 90 percent of adults in developed countries have been exposed to EBV by age 30, and moderately elevated antibody titers have not been associated with any EBV-related disease. The medical community eventually decided that chronic EBV is an inappropriate label for this illness.

Human Herpesvirus (HHV)-6 and -7
Some viruses, like HHV-6  and -7, can live in a dormant state inside the human body. There is evidence that HHV-6 and -7 get "reawakened" in patients with CFIDS.^6,7 These viruses have also been linked to multiple sclerosis (MS), an illness that shares many clinical features with CFIDS.⁷ But not all researchers have found a connection. Scientists at the U.S. Centers for Disease Control and Prevention, for example, have found no evidence that active or latent infection with HHV-6 or -7 is associated with CFIDS.⁹

The role of human herpesviruses in CFIDS, MS and other illnesses remains controversial, and it is difficult to compare studies due to the different methodologies used to detect the viruses. The question still remains whether the reawakened virus, if present, is the cause of the physical damage and resulting symptoms or the result of the illness.

Retroviruses
Retroviruses are known to cause uncommon neurological disorders that have a relapsing and remitting pattern similar to CFIDS. In 1991, a team of researchers led by Dr. Elaine DeFreitas published evidence suggesting that a human T lymphocytic virus type II (HTVL-II)-like retrovirus was present in the lymphocytes of CFIDS patients and might be the cause of their symptoms.¹⁰ Other preliminary evidence of possible retroviral involvement in CFIDS has been published. Dr. W. John Martin of California reported an association of CFIDS with a "stealth virus." ¹¹ Dr. Sidney Grossberg of Wisconsin discovered a new virus, called the "JHK" virus, in a CFIDS patient. Subsequent study by other laboratories has failed to reproduce any of these results.^{12, 13, 14}

Enteroviruses
Researchers in the United Kingdom have focused on enteroviruses, which include polio and Coxsackie virus, as a possible cause of CFIDS. So far, there has been no conclusive genetic evidence for the presence of enterovirus in CFIDS patients.^{15, 16} The results of muscle biopsies do not rule out enterovirus as a causative agent, but suggest that CFIDS is not dependent on a persistent enterovirus infection.¹

Cardiac Infection
Dr. Martin Lerner, an infectious disease specialist and clinical professor at Wayne State University School of Medicine, has suggested a possible connection between CFIDS and continuing or reactivated cardiac infection by EBV or cytomegalovirus.¹⁷ Dr. Lerner presented data to back up his theory at an international medical meeting in October 2000. He reported that in two small studies, 95 percent of CFIDS patients tested by holter monitoring had subnormal electrocardiograms indicating heart damage.¹⁸ It is important to keep in mind that these studies involved a small number of patients and have not been peer reviewed or published in mainstream medical literature. In addition, the cardiac abnormalities are described as mild and showed up in a high percentage of controls.

Mycoplasmas
In addition to viruses, other microorganisms such as mycoplasmas have been studied as possible causal agents for CFIDS. Mycoplasma are primitive forms of bacteria that have been identified in the blood of some CFIDS patients and veterans with Gulf War Illnesses, which present with many of the same symptoms.

A few laboratories claim that they are finding a high rate of mycoplasmal blood infections in CFIDS, fibromyalgia and Gulf War illness patients,¹⁹ but those findings have not been published in scientific literature. Mycoplasmas are difficult to detect in patients' blood, requiring very sensitive tests and careful handling of samples, making research difficult. The Veterans Affairs (VA) Administration is currently funding a clinical trial at 30 VA centers to look for mycoplasmas in Gulf War veterans' blood before and after a year of treatment with doxycycline, an antibiotic.

Role of viral testing in diagnosis
Because research has documented no clear association between a virus and CFIDS, testing patients for viral infection has limited use unless clinical signs indicate that an active viral infection may be present and requiring treatment. The results are also difficult to interpret, because the immune system in CFIDS may be up-regulated and latent viruses may not be fully suppressed.

Tests to determine elevated antibody titers for EBV and other viruses are not considered diagnostic for CFIDS by most physicians, and are usually performed only when a specific viral infection is suspected as a cause of the patient's symptoms.

Articles of Information

• Cardiac Involvement in CFS Studied
• HHV-6 
• The Role of Laboratory Tests in Diagnosis of Chronic Fatigue Syndrome
  By Charles W. Lapp, MD

Related Information

• Case Definition
• Research

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