A Centers for Disease Control and Prevention (CDC) review from review of the Salmonella Saintpaul outbreak of 2008, one of the largest outbreaks of foodborne illness reported in the U.S. to date, highlights a number of challenges facing epidemiologic investigation of such outbreaks.
According to lead author Casey Barton Behravesh, DVM, a veterinary epidemiologist with the CDC’s outbreak response and prevention branch, the OutbreakNet Team, such challenges include:
• epidemiologic identification of ingredients in foods that are commonly consumed;
• rapid identification and investigation of local clusters;
• the need to continue exploring hypotheses during an ongoing outbreak; and
• produce tracing in the supply chain.
The outbreak, which involved at least 1,500 cases, was originally attributed to tomatoes in salsa eaten at Mexican-style restaurants. Later studies determined that the culprits were actually jalapeño and serrano peppers.
“One of the main challenges that we have in all of our outbreak investigations is time,” Barton Behravesh said. “If someone eats contaminated food, it can take several days before they become ill. Then they may or may not go to the doctor, who may or may not take a stool sample. If they do, it can take up to three days before the pathogen is identified. Once it’s identified, it has to be shipped to a lab for serotyping and DNA fingerprinting. This whole process can take two to three weeks. So it becomes a challenge when we have to call and ask someone to recall the foods they ate in the week before they became ill, almost a month ago.”
In response, Barton Behravesh said, the CDC is trying to improve the capacity of its OutbreakNet Sentinel Sites. This pilot project, launched in summer 2009, involves a collaboration between the CDC, the U.S. Department of Agriculture’s Food Safety Inspection Service (FSIS), and the Association of Public Health Laboratories. “The goal is to improve our capacity and methods to investigate foodborne disease outbreaks,” she explained. “The sites, selected through a competitive process, will develop methods to speed the investigation of multistate outbreaks of enteric diseases like Salmonella, E. coli, and Listeria.”