The cause of CFS still eludes researchers but they continue to strive to find the answers to the mysterious disabling illness. In the Medical Hypotheses, (Apr 24 2008 [E-publication ahead of print] PMID: 18440157) by Grinde B. National Institute of Public Health in Norway, it is suggested that maybe CFS is caused by virus that is normally benign in most people – a circovirus.
Circoviruses are chronically present in most people but these are rarely tested for by physicians. As a rule, these viruses do not enter the brain but exceptions have been reported, and related viruses cause disease in animals’ central nervous systems.
The flu-like illness that often precedes the onset of CFS may either suppress immune function, causing an increased viremia, and/or lower the blood-brain barrier. In both cases the result may be that a virus already present in the blood enters the brain. It is well known that zoonotic viruses typically are more malignant than viruses with a long history of host-virus evolution. Similarly, a virus reaching an unfamiliar organ may cause particular problems.
Zoonotic viruses are viruses that are transmissable from animals to humans.