A new paper in Science shows that an acute gastroinstestinal infection of mice with Toxoplasmosis Gondii can lead to an immune reaction against some commensal (friendly/symbiotic) bacteria. Perhaps this could could go some way to explain how gastrointestinal infections can trigger IBS. There is quite a lot of evidence that IBS is much more likely to occur after a gastrointestinal infection e.g. the Giaida parasite. There is a study comparing 'functional somatic syndromes' CFS and IBS, finding that while there were 'many similar predisposing factors', viral infections were more likely to trigger CFS and gastrointestinal infections trigger IBS. Just maybe IBS, a 'functional somatic' gut disorder is triggered by a gut infection because there is a biological link between the initial gut infection and subsequent gut disorder? The Science paper above suggests one possible biological mechanism that might be involved.