Case-control method for seeking evidence of contagion in Crohn's disease.

All cases of Crohn's disease in the Nottingham area were ascertained and dates and places of domicile and work before and after onset of symptoms were noted. Similar information was taken from matched control subjects and the Pike and Smith (Biometrics 30:263-279, 1974) case control technique for evaluating clustering of patients in time and space was applied. These results do not support the infectious hypothesis.