What to know
During an enteric disease outbreak investigation, student interviewers can be critical in identifying outbreaks that may otherwise go undetected. This was the case for the Louisiana OutbreakNet Enhanced (OBNE) site during a Salmonella outbreak investigation caused by a rare serotype.
Louisiana Peels Back Salmonella Investigation's story
In April 2023, an OBNE student interviewer identified a cluster of cases located within the same city in Louisiana. The Louisiana State Public Health Laboratory notified investigators that Salmonella Oslo caused the illnesses. After performing whole genome sequencing (WGS) analysis, the cluster was established as outbreak.
After identifying the outbreak, follow-up interviews were performed with case-patients to identify common exposures. Through the interviews, investigators identified "Restaurant A" and boiled crawfish as the suspected source of the outbreak. As the investigation continued, one of the identified case-patients also tested positive for Vibrio. Epidemiologists worked with the environmental health team to assess Restaurant A.
Two assessments were conducted at Restaurant A: during the first visit, investigators found sources of cross-contamination. In the second, they observed workers prepare and store crawfish. Through these observations, investigators noticed crawfish being stored in a cracked, older cooler before being served to customers. Although samples taken from the cooler didn't yield Salmonella, investigators believed the cooler could be a source of contamination because it couldn't be completely cleaned due to the cracks. Restaurant A replaced the cooler in question, and no additional Salmonella cases have since been associated with the restaurant.
The investigation had limitations that made the outbreak difficult to solve. Many case-patients couldn't be reached for an interview and others couldn't remember where they ate crawfish. The environmental health team did not have all the equipment needed. Despite these difficulties, investigators worked together and successfully identified the outbreak during a busy crawfish season Investigators were also able to provide recommendations to Restaurant A to stop this outbreak and prevent recurrence.
Conclusion
The OBNE student interviewers were essential in identifying this unique Salmonella Oslo outbreak. With their help, investigators quickly identified the source of the outbreak and implemented control measures. Before the student team was formed, these case-patients may not have been quickly interviewed and the outbreak may have gone undetected. Enhanced resources for enteric disease programs, such as student teams, are critical for the safety of people's food, water, and environment.