UK researchers found that excessive immune response can trigger long-term fatigue, which indicates that CFS – also known as myalgic encephalomyelitis (ME) – begins.
Limited insight to date has made the treatment a challenge.
Pariante explained that patients in a lot of CFS cases remember an infection, such as a very bad cold or other viral infection, in the early stages of developing the condition.
"We had this information for quite some time, but did not know what was happening in these patients' bodies," he said.
To try to find out more about CFS, the team modeled a possible pathway to the condition based on a treatment for chronic hepatitis C infections called interferon alfa, as treatment is known to induce persistent fatigue in some people.
Interferon alfa affects the immune system in the same way as a strong infection, explains the study.
Researchers measured fatigue and immune activity in 55 patients receiving hepatitis C with interferon alfa.
Patients were followed up before, below and after treatment with hepatitis C. Of the participants, 18 patients developed – approximately one third – sustained fatigue, defined as fatigue lasting longer than six months after treatment.
The group of lasting fatigue also experienced a greater immune response – demonstrated by doubling in the levels of immune system messenger molecules interleukin-10 and interleukin-6.
Immune markers were measured with a blood sample during the study.
The team also saw higher levels of these molecules in these patients before treatment had even begun.
"What these data strongly suggest is that people who develop CFS in response to an infection, they do because their immune system is the priming for hyperreaction," explains Pariante. Why a person's immune system could be primed to hyperreaction is unclear, but genetics could be a possible reason, he added.
Patients are often diagnosed with CFS five, six or even up to 10 years later, according to Pariante, because the diagnosis is entirely based on symptoms, such as headache, chronic fatigue, difficulty in concentrating and inability to participate in activities.
At the time of diagnosis, patients would have been ill for a long time and did studies in the biology of people who develop the disease difficult, he added.
Dr. Charles Shepherd, medical advisor to the ME association in Britain, stated in an email that "many doctors still do not know how to diagnose and manage ME / CFS."
Shepherd, who was not involved in the study, said that a lack of research means "we still have no effective forms of treatment."
Shepherd said the study "adds to the growing importance of scientific evidence that the body's immune system plays an important role in the cause of ME / CFS."
The model team used for the study "is relevant to the two common causes" of CFS, says Pariante: a strong infection and a big stressful life event.
The study also found that "have quite severe acute fatigue during an infection or shortly after infection "makes people more at risk of developing CFS, he added.
Pariante hopes to once ask why this happens, of course, future treatments and screening can be identified.
The small sample size of the study was cited as a limitation of Pariante. More studies are needed to confirm its relevance to CFS patients, says the paper.
Skye Wheeler, a 19 year old from Cambourne, Cornwall, is home because of her ME / CFS.
"You can not get dressed and ready for the day without black falling over your eyes. You can not carry a conversation, let alone speak alone," she explained in a statement.
"At the bottom of the line there is no energy there primarily to channel through your body to all the right places. All you can do is lie and exist," she said.
The conditions affect many body systems, and people with chronic fatigue syndrome feel weakening pain and fatigue because their body and brain can not recover even after small efforts.
About a quarter of people affected by CFS / ME are severe cases, meaning they are bed-worn, housebound or wheelchair-bound sometime in their illness, according to the ME association.