Dr Bernie Hudson
Microbiology and Infectious Diseases,
Royal North Shore Hospital,
Chronic Fatigue Syndrome and Infectious Diseases
Chronic fatigue syndrome (CFS) is diagnosed after a number of medical conditions including active, relapsing or untreated infection are excluded. The eventual outcome of infection with any agent is determined by the host immune response to that agent. Symptoms caused by active infection may be indistinguishable from those due to persistent harmful immune responses, despite eradication of the infectious agent. The Center for Disease Control and Prevention (CDC) criteria list a number of infectious diseases that must be excluded in order to diagnose CFS. Whilst this seems straightforward, it definitely is not. Confounding factors which will be discussed include the following:
- The CDC lists only a limited number of diseases which require exclusion. Therefore, untreated, as yet undescribed, or poorly characterised infectious diseases could be causing illness despite the diagnosis of CFS. Examples include mycoplasma, rickettsia, and human herpesvirus infections. The exact status of such infections remains to the determined.
- Tests for some of these infections may have significant problems with false negative and false positive results. Previous infection with some agents may not have caused a detectable antibody response e.g. spirochetal infections such as leptospirosis, Lyme disease, some rickettsioses and some arbovirus infections.
- Tests for many infections may be unable to determine whether infection has resolved, or is persistent and causing illness e.g. Ross River and Barmah Forest virus infections, herpesviruses such as EBV, CMV, HHV.
- There may be no specific therapy for the infection, nor one that can guarantee virtually 100% cure rates, Additionally, many antimicrobial therapies have immunomodulating actions which make response to empiric therapy difficult to interpret.
All these factors require consideration in attempting to exclude possible treatable infectious causes of the individual's illness.
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