Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 3. Factors contributing to outbreaks and description of outbreak categories.

In this article, the third in a series of several reviewing the role of food workers in 816 foodborne outbreaks, factors contributing to outbreaks and descriptions of different categories of worker involvement are discussed. All the outbreaks had worker involvement of some kind, and the majority of food workers were infected. The most frequently reported factor associated with the involvement of the infected worker was bare hand contact with the food followed by failure to properly wash hands, inadequate cleaning of processing or preparation equipment or utensils, cross-contamination of ready-to-eat foods by contaminated raw ingredients, and (for bacterial pathogens) temperature abuse. Many of the workers were asymptomatic shedders or had infected family members and/or used improper hygienic practices. Outbreaks were sorted into categories based on how many workers were implicated, the origin of the infective agent (outbreak setting or off site), the degree of certainty that the worker(s) were the cause or were victims, whether or not the workers denied illness, the ability of the agent to grow in the food, whether only the workers and not the patrons were ill, and whether patrons were more responsible for their illnesses than were the workers. The most frequent scenarios were (i) a single worker causing an outbreak by directly infecting patrons; (ii) an infected worker fecally contaminating foods that were then temperature abused, leading to an outbreak; and (iii) multiple workers linked to an outbreak but with no clear initiating source. Multi-ingredient foods with limited descriptions were most frequently implicated and usually were served in restaurants or hotels, at schools, and at catered events. Identified contaminated ready-to-eat foods included produce, baked goods, beverages, and meat and poultry items. In some situations, it was not clear whether some of the workers were the cause or the victims of the outbreak. However, in other situations there may have been an underestimation of the role of the worker. For instance, workers sometimes denied infection or illness for a variety of reasons, but subsequent investigation provided evidence of infection.