The lack of heating immediately prior to consumption elevates the risk for listeriosis;
if an initial contamination by L. monocytogenes happens, no further inactivation steps are usually involved. Several studies have pointed to the post-processing manipulations as important factors for the presence of L. monocytogenes the retail site has been identified to be one
of the important places for cross-contamination. In a large-scale survey of RTE foods collected from retail markets in the U.S. (2003) found that in-store-packaged deli meats were more likely to harbor L. monocytogenes than were manufacturer-packaged products.