All CoE Products website:
During a restaurant outbreak investigation, it can often be challenging to obtain patron contact information (i.e. credit card receipts, online orders, or reservations) from the restaurant. Providing a letter explaining the public health authority to collect this information is one way to increase cooperation from the restaurant.
During PFGE cluster investigations, cases may not answer phone calls or initially refuse to be interviewed. Sending a letter explaining that they are most likely part of an outbreak can increase interview participation.
CDC Integrated Food Safety Centers of Excellence:
More information about food safety: