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Incidence of Post-Infectious Irritable Bowel Syndrome and Functional Intestinal Disorders Following a Water-Borne Viral Gastroenteritis Outbreak

Zanini, Barbara MD, PhD1; Ricci, Chiara MD, PhD1; Bandera, Floriana MD2; Caselani, Francesca MD1; Magni, Alberto MD1; Laronga, Anna Maria1; Lanzini, Alberto MD, PhD1 for the San Felice del Benaco Study Investigators

American Journal of Gastroenterology: June 2012 - Volume 107 - Issue 6 - p 891–899
doi: 10.1038/ajg.2012.102
Functional GI Disorders

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'st-test andχ2- 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.

1 Department of Medical and Surgical Sciences, Gastroenterology Unit, University and Spedali Civili of Brescia, Brescia, Italy

2 Department of General Medicine, Local Health Authority, Brescia, Italy

3 See Appendix

Correspondence: Alberto Lanzini, MD, PhD, Department of Medical and Surgical Sciences, Gastroenterology Unit, University and Spedali Civili of Brescia, Piazzale Spedali Civili 1, Brescia I-25123, Italy. E-mail:

Received 4 July 2011; accepted 16 November 2011

published online 24 April 2012

© The American College of Gastroenterology 2012. All Rights Reserved.
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