With E. coli O157:H7, more tests are conducted each year. Thankfully, the vast majority of the results have been negative, but there are still positive findings.
In some cases, a high number of findings on a particular slaughter day may result in the questioning of the negative findings and whether the intact product, not customarily tested, is also implicated (“an event”). In other cases, a downstream test may implicate product that had previously been found negative and shipped to other facilities (in this case, the certificate of analysis (COA) sent with the product is no longer valid in light of the new positive finding).