As for genetics issues in PI-IBS cases, a follow-up study performed after a waterborne outbreak of gastroenteritis in Walkerton, Canada demonstrated that single nucleotide polymorphisms in Toll-like receptor (TLR)9, Interleukin (IL)-6, and Cadherin-1 were independent genetic risk factors for PI-IBS development (19). This evidence concerns the gene TLR9 and gastroenteritis.