Breaking the Egg Case
Doug Powell below writes in his Barfblog about the delay in CDC notifying the public about the source of the current SE outbreak in eggs. The CDC went public in mid August when apparently sufficent information existed in late July to implicate Iowa's Wright Egg Farms.
Other outbreaks in the recent past had the same scenario, a delay between identifying the likely source of outbreaks and public disclosure.
There might be a couple of explanations for the delay in the naming of names as a result of epidemiological findings. The strength of the epidemiological data sometimes is not strong enough to make confirmation completely bullet proof, remember we are dealing with relative risk.
Second, when an agency goes public they can be wrong and end up with well...egg on their faces, and much worse.
On the other hand, when there is a strong likelihood of a public health threat there might be good reason to go public even if all data crunching is not complete, a common supplier is certainly suspicious. I agree with Doug, the key is the strength of the data.
Egg is one of the common source of many diseases such as salmonella (typhoid).