A Norwegian study shows that at least 5% of the patients with confirmed Giardia enteritis following an outbreak in 2004 in Bergen failed to recover. The unexplained fatigue and accompanying symptoms corresponded in the main with other post-infectious fatigue syndromes.
In comparison, the prevalence of CFS in a normal population ranges between 0.23% and 0.56% in different populations. Thus, the frequency of CFS among patients with confirmed Giardia infection was at least 8 times higher than in the general population. The findings suggest that there may be a relationship between Giardia infection and CFS.
Although the cause of CFS is unknown it is generally thought that post-infectious fatigue develops shortly after acute infection however, more than half of the patients studied had a gradual onset of fatigue. Patients who developed fatigue over months, tended to have more initial abdominal symptoms than patients who developed fatigue within weeks of Giardia enteritis. A possible explanation is that many initial symptoms either masked the experience of early fatigue or the recall of early fatigue among some patients. This may be of special importance in cases of litigation where the timing of fatigue onset after acute infection may determine the question of causation.
