title: Incidence of post-infectious irritable bowel syndrome and functional intestinal disorders following a water-borne viral gastroenteritis outbreak.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Medical and Surgical Sciences, Gastroenterology Unit, University and Spedali Civili of Brescia, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Zanini
authors.forename: Chiara
authors.initials: C
authors.lastname: Ricci
authors.forename: Floriana
authors.initials: F
authors.lastname: Bandera
authors.forename: Francesca
authors.initials: F
authors.lastname: Caselani
authors.forename: Alberto
authors.initials: A
authors.lastname: Magni
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Laronga
authors.forename: Alberto
authors.initials: A
authors.lastname: Lanzini
mesh_terms: D015746:Abdominal Pain / Q000209:etiology; D000208:Acute Disease; D000328:Adult; D000368:Aged; D017250:Caliciviridae Infections / Q000150:complications / Q000453:epidemiology* / Q000821:virology; D002908:Chronic Disease; D003248:Constipation / Q000209:etiology; D003967:Diarrhea / Q000209:etiology; D004196:Disease Outbreaks; D060766:Drinking Water / Q000821:virology*; D004415:Dyspepsia / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D005759:Gastroenteritis / Q000150:complications / Q000453:epidemiology* / Q000821:virology*; D005764:Gastroesophageal Reflux / Q000209:etiology; D006801:Humans; D015994:Incidence; D043183:Irritable Bowel Syndrome / Q000150:complications* / Q000453:epidemiology / Q000821:virology*; D007558:Italy / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D029322:Norovirus / Q000302:isolation & purification*; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013997:Time Factors; D014871:Water Microbiology
chemical_list: D060766:Drinking Water