2004 Bergen, Norway outbreak

In 2004, in Bergen, Svartediket, Norway, an outbreak of chronic fatigue syndrome followed a contamination of the water supply with the parasite Giardia lamblia.

Of the 1252 people sickened by Giardia, 253 scored high enough on the Chalder fatigue scale to be invited in a follow-up study five years later by Haukeland University Hospital and University of Bergen, Norway. Of those invited, 53 participated. The study concluded that 41.5% of the participants had chronic fatigue syndrome and 13.2% had Idiopathic Chronic Fatigue according to the Fukuda criteria.

The patient cohort continues to be studied by the University of Bergen and Haukeland University Hospital.

Follow-up studies
"Conclusion: Patients with PI-CFS and/or PI-FGID 5 years after Giardia lamblia infection showed alterations in NK-cell and CD8-cell populations suggesting a possible immunological abnormality in these conditions. We found no significant changes in other markers examined in this well-defined group of PI-CFS and PI-FGID elicited by a gastrointestinal infection. Controlling for co-morbid conditions is important in evaluation of CFS-biomarkers." Abstract - Background: Municipal drinking water contaminated with the parasite Giardia lamblia in Bergen, Norway, in 2004 caused an outbreak of gastrointestinal infection in 2500 people, according to the Norwegian Prescription Database. In the aftermath a minor group subsequently developed post-infectious fatigue syndrome (PIFS). Persons in this minor group had laboratory-confirmed parasites in their stool samples, and their enteritis had been cured by one or more courses of antibiotic treatment. The study's purpose was to explore how the affected persons experienced the illness trajectory and various PIFS disabilities. Methods: A qualitative design with in-depth interviews was used to obtain first-hand experiences of PIFS. To get an overall understanding of their perceived illness trajectory, the participants were asked to retrospectively rate their functional level at different points in time. A maximum variation sample of adults diagnosed with PIFS according to the international 1994 criteria was recruited from a cohort of persons diagnosed with PIFS at a tertiary Neurology Outpatient Clinic in Western Norway. The sample comprised 19 women and seven men (mean age 41 years, range 26-59). The interviews were fully transcribed and subjected to a qualitative content analysis. Results: All participants had been living healthy lives pre-illness. The time to develop PIFS varied. Multiple disabilities in the physical, cognitive, emotional, neurological, sleep and intolerance domains were described. Everyone more or less dropped out from studies or work, and few needed to be taken care of during the worst period. The severity of these disabilities varied among the participants and during the illness phases. Despite individual variations, an overall pattern of illness trajectory emerged. Five phases were identified: prodromal, downward, turning, upward and chronic phase. All reached a nadir followed by varying degrees of improvement in their functional ability. None regained pre-illness health or personal and professional abilities.
 * 2012, Immunophenotyping in post-giardiasis functional gastrointestinal disease and chronic fatigue syndrome - (Full text)
 * 2013, Chronic fatigue syndrome 5 years after giardiasis: differential diagnoses, characteristics and natural course - (Full text)
 * 2017, Giardia-specific cellular immune responses in post-giardiasis chronic fatigue syndrome - (Full text)
 * 2017, From good health to illness with post-infectious fatigue syndrome: a qualitative study of adults’ experiences of the illness trajectory (Full text)

Conclusion: The needs of persons with this condition are not met. Early diagnosis and interdisciplinary rehabilitation could be beneficial in altering the downward trajectory at an earlier stage, avoiding the most severe disability and optimising improvement. Enhanced knowledge among health professionals, tailored treatment, rest as needed, financial support and practical help would likely improve prognosis. Results: The prevalence of IBS 10 years after the outbreak was 43% (n = 248) among 576 exposed individuals and 14% (n = 94) among 685 controls (adjusted odds ratio for development of IBS in exposed individuals, 4.74; 95% CI, 3.61–6.23). At this time point, the prevalence of chronic fatigue was 26% (n = 153) among 587 exposed individuals and 11% (n = 73) among 692 controls (adjusted odds ratio, 3.01; 95% CI, 2.22–4.08). The prevalence of IBS among exposed persons did not change significantly from 6 years after infection (40%) to 10 years after infection (43%; adjusted odds ratio for the change 1.03; 95% CI, 0.87–1.22). However, the prevalence of chronic fatigue decreased from 31% at 6 years after infection to 26% at 10 years after infection (adjusted odds ratio for the change 0.74; 95% CI, 0.61–0.90). Conclusion: The prevalence of IBS did not change significantly from 6 years after an outbreak of Giardia lamblia infection in Norway to 10 years after. However, the prevalence of chronic fatigue decreased significantly from 6 to 10 years afterward. IBS and chronic fatigue were still associated with giardiasis 10 years after the outbreak.
 * 2018, Prevalence of Irritable Bowel Syndrome and Chronic Fatigue 10 Years After Giardia Infection - (Full text)