Incidence of post-infectious irritable bowel syndrome and functional intestinal disorders following a water-borne viral gastroenteritis outbreak

Am J Gastroenterol. 2012 Jun;107(6):891-9. doi: 10.1038/ajg.2012.102. Epub 2012 Apr 24.


Objectives: Post-infectious irritable bowel syndrome (PI-IBS) may develop in 4-31% of affected patients following bacterial gastroenteritis (GE), but limited information is available on long-term outcome of viral GE. During summer 2009, a massive outbreak of viral GE associated with contamination of municipal drinking water (Norovirus) occurred in San Felice del Benaco (Lake Garda, Italy). To investigate the natural history of a community outbreak of viral GE, and to assess the incidence of PI-IBS and functional gastrointestinal disorders, we carried out a prospective population-based cohort study with a control group.

Methods: Baseline questionnaires were administered to the resident community within 1 month of the outbreak. Follow-up questionnaires of the Italian version of Gastrointestinal Symptom Rating Scale (GSRS, a 15-item survey scored according to a 7-point Likert scale) were mailed to all patients responding to baseline questionnaire at 3 and 6 months, and to a cohort of unaffected controls, living in the same geographical area, at 6 months after the outbreak. The GSRS item were grouped in five dimensions: abdominal pain, reflux, indigestion, diarrhea, and constipation. At month 12, all patients and controls were interviewed by a health assistant to verify Rome III criteria of IBS. Student's t-test and χ(2)- or Fisher's exact test were used as appropriate.

Results: Baseline questionnaires were returned by 348 patients: mean age ± s.d. 45 ± 22 years, 53% female. At outbreak, nausea (scored ≥4), vomiting, and diarrhea lasting 2-3 days or more were reported by 66, 60, and 77% of patients, respectively. A total of 50% reported fever and 19% reported weight loss (mean 3 kg). Follow-up surveys were returned at month 6 by 186 patients and 198 controls: mean GSRS score was significantly higher in patients than in controls for abdominal pain, diarrhea, and constipation. At month 12, we identified 40 patients with a new diagnosis of IBS (Rome III criteria), in comparison with 3 subjects in the control cohort (P<0.0001; odds ratio 11.40; 95% confidence intervals 3.44-37.82). The 40 cases of PI-IBS were subtyped according to the predominant stool pattern as follows: 4 IBS with constipation, 7 IBS with diarrhea, 16 with mixed IBS, and 13 with unsubtyped IBS.

Conclusions: Our study provides evidence that Norovirus GE leads to the development of PI-IBS in a substantial proportion of patients (13%), similar to that reported after bacterial GE.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abdominal Pain / etiology
  • Acute Disease
  • Adult
  • Aged
  • Caliciviridae Infections / complications
  • Caliciviridae Infections / epidemiology*
  • Caliciviridae Infections / virology
  • Chronic Disease
  • Constipation / etiology
  • Diarrhea / etiology
  • Disease Outbreaks*
  • Drinking Water / virology*
  • Dyspepsia / etiology
  • Female
  • Follow-Up Studies
  • Gastroenteritis / complications
  • Gastroenteritis / epidemiology*
  • Gastroenteritis / virology*
  • Gastroesophageal Reflux / etiology
  • Humans
  • Incidence
  • Irritable Bowel Syndrome / complications*
  • Irritable Bowel Syndrome / epidemiology
  • Irritable Bowel Syndrome / virology*
  • Italy / epidemiology
  • Male
  • Middle Aged
  • Norovirus / isolation & purification*
  • Severity of Illness Index
  • Surveys and Questionnaires
  • Time Factors
  • Water Microbiology


  • Drinking Water