Which of the following indicates that an outbreak of foodborne illness is over?

The indication that an outbreak of foodborne illness is over is when all suspect food has been consumed or recalled. This is a critical step in the food safety response as it directly addresses the source of potential contamination. If the food that is suspected to be linked to the illness is no longer available, it effectively eliminates the risk of further spreading the illness connected to that food item.

In a foodborne illness investigation, once the suspected foods are accounted for and either consumed or properly recalled, public health officials can more confidently assess that the outbreak has been contained. It allows for further analysis of the outbreak's causes without the ongoing threat of infected food still being in circulation.

The other options, while related to food safety practices, do not definitively indicate that an outbreak has concluded. Improved staff training, increased inspections, and more training sessions can all contribute to preventing future outbreaks, but they do not confirm the end of the current outbreak. The conclusive measure is the removal of the hazardous food items from consumption.