The role of infectious agents in Crohn's disease.

Environmental factors certainly play a role in the appearance of Crohn's disease. Wether or not those factors are infectious agents remains uncertain. Broadly, two classes of infectious hypothesis are currently under investigation. The first one, concerning specific microorganisms (such as mycobacteria and virus) dates back to the first description of the disease in 1913. The second one studies the possible involvement of compounds derived from the intestinal microflora, irrespective to speciation. It appeared more recently and receives more and more attention. These hypothesis are reviewed by the authors with regard to data obtained from epidemiology, clinical and experimental investigations.