What causes Crohn's disease?

According to Crohn's and Colitis Foundation of America (CCFA)'s brochure "Questions and Answers About Crohn's Disease" (Publication 1015, the current one is from 1997):

"Researchers do not know what causes this disease. They do not believe it is caused by emotional stress or by food, or that it is transmitted directly from person to person. ... Many scientists now believe that the interaction of an outside agent (such as virus or bacterium) with the body's immune system may trigger the disease, or that such an agent may cause damage to the intestinal wall, initiating or accelerating the disease progress."

Epidemiological studies of communicable (infectious) diseases (note that CCFA's statement deliberately avoids mentioning the word "infectious" to prevent public panic, although agents like viruses or bacteria that provoke a disease are nothing but infectious) have defined the following routes of transmission:

CCFA's statement is again very cautious when saying that researchers do not believe Crohn's disease is transmitted directly from person to person, which leaves a possibility of indirect transmission via fecal-oral foodborne route. Indeed, knowing the spatial and temporal trends of Crohn's epidemiology, one can eliminate as possible most of the routes above. We know that Crohn's is not a venereal disease because a certain percentage of patients is too young for this route of transmission. Since it is not a highly communicable disease like fly, we can also discard direct contact or aerosol route. Crohn's disease is not endemic like malaria, making it less likely that it is a vector borne (mosquito as vector in malaria) disease. A study from Holland (Gastroenterology, 1987 Nov, 93:5, 966-74) has examined the theory of water borne transmission, but found no evidence that different water supplies influenced incidence rates in urban and agrarian communities. Since it has not been noticed that Crohn's disease occurs more frequently in pet owners or professions that have daily contact with animals, zoonoses route is also unlikely.

In the view of fecal-oral foodborne route, I felt uneasy reading FDA's Food Code (Chapter 2-201.13.) that allows Crohn's patients to work in restaurants and other places where food is handled. Doesn't Crohn's prevalence among young, single people (that eat out more often than married people who are predominant in the age group less affected with Crohn's) point in the direction of foodborne transmission? I do have some additional clues to support this theory (drawn from more than 70 papers reporting regional incidence of Crohn’s disease throughout the world, published in past 35 years), but can not discuss them here since they are in the form of a research paper currently under review for publishing in a medical journal.

Please be aware that my claims were not meant to offend Crohn's patients (since I may be in the
same boat), but to make them aware that they may present a potential risk for genetically
predisposed persons, and even more for their loved ones (since they share the most genetic
similarities with them). I am just trying to make them more cautious and  aware of cleanliness when
preparing food, sharing soap and other household occasions where transmission may occur.

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