that childhood CD has features of an infectious disease with a peak incidence between 1985 and 1996 in children younger than 2 years of age, a period referred to as ‘the Swedish CD epidemic’ (Ivarsson et al., 2000). A similar increase in incidence was seen later, during 2001–2004 (Olsson et al., 2008; Namatovu, F. et al., unpublished data). After both peaks, incidence returned to normal. We have shown that CD patients born during ‘the Swedish CD epidemic’ had a significant enrichment of mucosa-associated rod-shaped bacteria of the order Clostridiales, and genera Prevotella and Actinomyces in the jejunum (Forsberg et al., 2004; Ou et al., 2009). Recently, we characterized a novel species of a new genus, Lachnoanaerobaculum umeaense, that had been isolated from the jejunal mucosa of a child born during ‘the Swedish CD epidemic’ (Hedberg