Many of the signs and symptoms of ME/CFS are similar to those of a lingering viral illness, so a lot of research has focused on the possibility of a viral or infectious cause. Researchers have examined three infection-related theories, though none has been proven:
However, some evidence seems to run counter to the viral-cause theory. ME/CFS doesn't appear to spread through direct content, people with it don't appear contagious, and -- in spite of well-designed studies -- researchers have not been able to link ME/CFS with any specific infections.
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- A virus or bacteria infects the body and damages the immune system. The damage then continues to cause flu-like symptoms even after the virus or bacteria is gone.
- After an infection, an abnormal action by the immune system triggers a virus that had become inactive to reactivate.
- A physiological response to viral infections occurs in people who are susceptible.
- Enterovirus connection In a 2007 study, people with ME/CFS were four times more likely than healthy people to have evidence of enteroviruses in their stomach tissues. Enteroviruses cause stomach infections, and symptoms of ME/CFS frequently start after that kind of illness.
- Rnase L Your body uses the enzyme Rnase L to kill viruses that are attacking your cells, and ME/CFS patients frequently have high Rnase L activity.
- Natural Killer (NK) Cells and T CellsNK & T cells in your immune system attack virus-infected cells, and people with ME/CFS frequently have impaired NK and T cell functions and numbers, suggesting chronic immune activity may be exhausting and depleting them.
- Antibodies People with ME/CFS typically have high levels of antibodies to many infection-causing organisms that cause fatigue and other ME/CFS symptoms. These organisms include those that cause candida (yeast), human herpesvirus type 6 (HHV-6), measles, parvovirus and Epstein-Barr. Researchers have not been able to show that any of these is a significant cause of ME/CFS.
- Post-illness onset Up to 80% of ME/CFS cases start suddenly after a flu-like condition.
- Cluster outbreaks While the CDC has not confirmed most cluster outbreaks, reports of multiple people in the same household, workplace and community developing ME/CFS at the same time are not unheard of.
However, some evidence seems to run counter to the viral-cause theory. ME/CFS doesn't appear to spread through direct content, people with it don't appear contagious, and -- in spite of well-designed studies -- researchers have not been able to link ME/CFS with any specific infections.
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