Controls - information from records of investigations, conducted during the previous 3 months, of other enteric illnesses from residents of the same 4 towns as our hepatitis A cases. 'Where do you usually do your grocery shopping ?' was a routinely-asked question for all enteric investigations.

One of 10 persons reported shopping at deli A. The use of information we had on hand enabled us to avoid alarming the public before we had all the information we needed. While it did not rule out the possibility that the break in the sewer line contributed to this outbreak, it certainly strengthened the our case for a foodborne outbreak. As subsequent cases were reported and investigated over the next several days, we encountered a number of persons who had visited the area and left prior to the main break. These “outliers” all had exposure to the involved deli and served to confirm our hypothesis.