Question

Since laboratory tests had confirmed Salmonella, a common foodborne pathogen, as the etiologic agent, epidemiologists suspected that the outbreak was caused by contamination at a food processing facility serving the region. Interviews with patients focused on food consumption during and after the Thanksgiving holiday, corresponding with the timing of the outbreak. During the interviews, patients were asked to list items consumed at holiday gatherings and describe how widely each item was consumed among family members and relatives. They were also asked about the sources of food items (e.g., brand, location of purchase, date of purchase). By asking such questions, health officials hoped to identify patterns that would lead back to the source of the outbreak.

Analysis of the interview responses eventually linked almost all of the cases to consumption of a holiday dish known as the turducken—a chicken stuffed inside a duck stuffed inside a turkey. Turducken is a dish not generally consumed year-round, which would explain the spike in cases just after the Thanksgiving holiday. Additional analysis revealed that the turduckens consumed by the affected patients were purchased already stuffed and ready to be cooked. Moreover, the pre-stuffed turduckens were all sold at the same regional grocery chain under two different brand names. Upon further investigation, officials traced both brands to a single processing plant that supplied stores throughout the Florida panhandle.

Is this an example of common source spread or propagated spread?

What next steps would the public health office likely take after identifying the source of the outbreak?

Answer 1

This outbreak will be classified as Common Source Outbreak. A common-source outbreak is defined on the basis of the source of infectious agent. When a group of people are exposed to an infectious agent or toxin which has same source, then the outbreak is defined as common source.

In cases when group develops illness in one incubation period, that is group is exposed to toxin over a brief period of time, then common-source outbreak is further classified as point-source outbreak.

Once the outbreak source is established, the public health office works towards controlling the outbreak and prevention of further spread. The primary goal of identifying the source of the outbreak is to efficiently control the outbreak. The control measure includes but not limited to seclusion of the affected people, effective treatment based on the data available about the cause and checking further spread of the infection.

Once control and prevention measures are established, public health office initiates the process of surveillance to check on re-occurrence of the outbreak. This includes establishment of monitoring systems.