{
  "schema_version": "2.0.0",
  "id": "bergen-giardiasis-2004",
  "name": "Bergen Giardiasis Cohort",
  "aliases": [
    "Bergen Giardia outbreak cohort"
  ],
  "outbreak_event": "Bergen giardiasis outbreak 2004 (Norway)",
  "pathogen_id": "giardia-duodenalis",
  "pathogen_class": "protozoan",
  "exposure_ascertainment": "mixed",
  "design": "retrospective_cohort",
  "denominator_defined": "yes",
  "denominator_method": "Individuals with laboratory-confirmed Giardia during the 2004 Bergen waterborne outbreak, compared with matched controls from the same population.",
  "recruitment_source": "population_registry",
  "time_zero_definition": "Laboratory-confirmed acute giardiasis during the 2004 outbreak",
  "time_zero_precision": "quarter",
  "control_group": "unexposed_matched",
  "control_matching_variables": [
    "age",
    "sex"
  ],
  "n_source_population": null,
  "n_enrolled": 1252,
  "n_analysed": 1252,
  "followups": [
    {
      "months": 36,
      "n_assessed": null,
      "n_lost": null
    },
    {
      "months": 72,
      "n_assessed": null,
      "n_lost": null
    },
    {
      "months": 120,
      "n_assessed": null,
      "n_lost": null
    }
  ],
  "max_followup_months": 120,
  "instruments": [
    "chalder-fatigue-scale",
    "rome-criteria-ibs"
  ],
  "case_definition": "chalder_threshold",
  "pem_assessed": "no",
  "objective_measures": [
    "none"
  ],
  "specimens_collected": false,
  "specimen_types": [],
  "acute_phase_specimens": "no",
  "storage": null,
  "biobank_status": "not_applicable",
  "consent_future_use": "unknown",
  "external_access": "unknown",
  "contact": null,
  "registration_id": null,
  "funders": [
    "Haukeland University Hospital / University of Bergen"
  ],
  "conflicts": null,
  "data_availability": null,
  "notes": "Controlled cohort with a matched unexposed comparator and unusually long follow-up (3, 6, and 10 years), demonstrating persistence of post-infectious IBS and chronic fatigue after a protozoan (non-viral) infection.",
  "publications": [
    {
      "id": "hanevik-2014",
      "title": "Irritable bowel syndrome and chronic fatigue 6 years after giardia infection: a controlled prospective cohort study",
      "authors": "Hanevik K, Wensaas KA, Rortveit G, et al.",
      "year": 2014,
      "journal": "Clinical Infectious Diseases",
      "doi": "10.1093/cid/ciu629",
      "pmid": "25115874",
      "url": "https://pubmed.ncbi.nlm.nih.gov/25115874/",
      "open_access": false,
      "is_primary_cohort_paper": true
    }
  ],
  "symptom_inventory_scope": "targeted_panel",
  "n_symptoms_queried": null,
  "symptom_instrument_note": null,
  "related_cohorts": [],
  "last_verified": "2026-07-20",
  "verified_by": "OSMF research-tracker (web-verified against source)",
  "harmonisation_ruleset": "pais-harmony-v1",
  "observations": [
    {
      "id": "bergen-ibs-6yr",
      "cohort_id": "bergen-giardiasis-2004",
      "publication_id": "hanevik-2014",
      "schema_version": "2.0.0",
      "measure_id": "sym:irritable-bowel-syndrome",
      "measure_verbatim": "irritable bowel syndrome 6 years after giardiasis",
      "population": {
        "scope": "whole_cohort",
        "stratum": null,
        "denominator_basis": "unclear",
        "n_assessed": {
          "status": "measured_not_reported"
        }
      },
      "timing": {
        "timepoint_months": 72,
        "timepoint_band": "24mo+",
        "reference_period": "not_reported",
        "is_cumulative": false
      },
      "method": {
        "ascertainment": "unclear",
        "instrument_id": "rome-criteria-ibs",
        "severity_threshold": null,
        "blinded_assessment": "not_reported"
      },
      "value": {
        "type": "proportion",
        "numerator": {
          "status": "measured_not_reported"
        },
        "denominator": {
          "status": "measured_not_reported"
        },
        "percent": 39.4,
        "ci": null,
        "precision": "approximate"
      },
      "comparator": {
        "group": "none",
        "value": {
          "status": "not_applicable"
        },
        "effect": null
      },
      "harmonised": null,
      "provenance": {
        "source_locator": "Results/Abstract (IBS 39.4% in exposed, significantly elevated vs controls)",
        "extracted_by": null,
        "extracted_on": null,
        "verified_by": "OSMF research-tracker (web-verified against source)",
        "verified_on": "2026-07-20",
        "extraction_method": "manual"
      }
    },
    {
      "id": "bergen-cf-6yr",
      "cohort_id": "bergen-giardiasis-2004",
      "publication_id": "hanevik-2014",
      "schema_version": "2.0.0",
      "measure_id": "sym:fatigue",
      "measure_verbatim": "chronic fatigue 6 years after giardiasis",
      "population": {
        "scope": "whole_cohort",
        "stratum": null,
        "denominator_basis": "unclear",
        "n_assessed": {
          "status": "measured_not_reported"
        }
      },
      "timing": {
        "timepoint_months": 72,
        "timepoint_band": "24mo+",
        "reference_period": "not_reported",
        "is_cumulative": false
      },
      "method": {
        "ascertainment": "unclear",
        "instrument_id": "chalder-fatigue-scale",
        "severity_threshold": null,
        "blinded_assessment": "not_reported"
      },
      "value": {
        "type": "proportion",
        "numerator": {
          "status": "measured_not_reported"
        },
        "denominator": {
          "status": "measured_not_reported"
        },
        "percent": 30.8,
        "ci": null,
        "precision": "approximate"
      },
      "comparator": {
        "group": "none",
        "value": {
          "status": "not_applicable"
        },
        "effect": null
      },
      "harmonised": null,
      "provenance": {
        "source_locator": "Results/Abstract (chronic fatigue 30.8% in exposed, significantly elevated vs controls)",
        "extracted_by": null,
        "extracted_on": null,
        "verified_by": "OSMF research-tracker (web-verified against source)",
        "verified_on": "2026-07-20",
        "extraction_method": "manual"
      }
    }
  ]
}