The anatomy of an outbreak

It starts with a report because somewhere someone was sick enough to either be admitted to a hospital or get their doctor concerned enough to check out why they were so sick.
Then another report. 
The second report should trigger an investigation, sometimes it does, some times not, but the third does.
Interviews are performed and a location that fits the time frame is uncovered.
Workers are then queried:
Is any one sick?  The response is usually a unified no.
More questions about what they do, when they work.
Then general food handling practice.
What do they work with?
Do they use gloves?
Do they wash their hands?
They all know the right answers, but occasionally some one blanches on a question nad we know the truth.
Stool samples are required of every worker.
They do not report all the people who work there, but samples form the workers come back positve.
Some confess they have been sick.  They know that if they are positive they will be out of work for at least 2 weeks.
The owner gets upsets, "we cook our chicken to 550 degrees!", he exclaims.
We look at each other and tell him it is not the chicken.  that it probably was someone who was sick working with out gloves on the salad.  he blanches and asks, gloves?  Salad?
A worker comes in, not on our list. 
They work nights. 
They were not told about the problem.
They have been sick.
They say everyone has been sick.
We know, we say.
More positive stools and now the restaurant is closed because all their workers test positive, even the owners.
We are told of people having been sick who ate there, but it is now a long while and they are okay.
When did it start?  We do not know.
How many people got sick?  A lot, many more than we will ever find.
Why. why don't they wash their hands?