Enteroviruses and the Possible Link to Chronic Fatigue Syndrome

Enteroviruses live and reproduce in your intestinal tract. They sometimes spread to other parts of the body, including the nervous system.

Humans are susceptible to more than 70 types of enteroviruses. They're extremely common—the only viruses that are more prevalent are those related to the "common cold." That means it's likely you've been exposed to some of them. However, that doesn't mean they've made you sick.

Specific enteroviruses can cause various diseases, including poliomyelitis, rashes, mouth sores, hepatitis, aseptic meningitis, and inflammatory lung and heart disease. Most enterovirus infections, though, do not lead to disease.

When they do make people sick, it's usually with a mild and cold-like illness or a flu-like illness that includes fever and muscle aches.

Flu-like symptoms are also common in people with chronic fatigue syndrome, and the onset of this disease often comes right after the person has had a flu-like illness. That has made some researchers hypothesize that these viruses could play a role in chronic fatigue syndrome.

For now, we can't say for certain whether an enterovirus infection could cause or contribute to an illness like chronic fatigue syndrome, but we do have some research pointing to a possible link:

• A 2008 study (Chia) showed a high predominance of enteroviruses in the guts of people with this disease, which researchers said could explain some of the common symptoms.
• A 2010 follow-up (Chia) suggested that acute infections of enteroviruses may lead to a "stalemate" situation between the virus and the immune system and that it may result in chronic fatigue syndrome.
• Another 2010 study (Zhang) linked enterovirus to a subtype of chronic fatigue syndrome and called enterovirus one of the two most common infectious triggers of the disease (along with the Epstein-Barr virus.)

Because the bodies of people with chronic fatigue syndrome show signs of an activated immune system, scientists have long believed that many cases are caused either by an active viral or bacterial infection or by an infection that permanently alters the immune system before leaving the body.