The 2015 Food Safety Summit went off without a hitch last week in Baltimore, MD, despite the social unrest occurring less than a mile from the city's Convention Center. 

Food safety professionals from all over the globe gathered to discuss ongoing issues, emerging trends and solutions affecting the industry. Throughout the 3-day event, one clear message resonated with attendees: food safety is a remarkably complex system, and it will take a village of academicians, growers, processors, manufacturers, distributors, retailers and consumers to continue to improve upon it.

While there was plenty of talk about food fraud, traceability, food waste and the Food Safety Modernization Act, perhaps the most intriguing session was given by Alvina Chu from the Maryland Department of Health and Mental Hygiene (DHMH). She gave an eye-opening overview of the foodborne outbreak that occurred at last year’s Food Safety Summit, also held at the Baltimore Convention Center.

What Happened
Chu started her talk by stating the obvious. “Last year’s outbreak was pure irony,” It was April 11, 2014. Baltimore’s local 311 phone service received three reports of illness, followed by a fourth report the next day. Each person said they’d attended the Food Safety Summit and subsequently became ill with diarrhea between April 8 and 10. On April 16, the Baltimore City Health Department began an outbreak investigation with help from the Maryland DHMH.

Epidemiologic Investigation
First, officials put together an online questionnaire that was sent via email to all registered Summit attendees. The survey included open-ended questions since exposure to the outbreak could have originated anywhere--perhaps a contaminated door knob, or a sick speaker who shook hands with many attendees. There was also a review of the food menu, scheduled sessions and activities that the sickened individuals may have partaken in.

Environmental Investigation
Officials launched an investigation into the unnamed caterer that served food--all buffet style--to last year’s 1,300 Summit attendees. This included food testing on some ingredients that were used to prepare dishes that were served to attendees. However, there were no leftovers from the event remaining to be tested. Instead, officials did review the food preparation methods and processes for all food items included on the Summit’s menu.

In a lab analysis, stool samples were tested for a vast number of pathogens:

  • Enteric bacteria: Salmonella, Shigella, STEC, Campylobacter, Clostridium perfringens
  • Viruses: Norovirus, Rotavirus, Astrovirus, Sapporo virus

Food samples were also cultured for Bacillus cereus and C. perfringens

Survey Says
The online survey garnered 669 responses, but not all of them could be factored into the investigation’s official findings. Why?

  • Some respondents reported falling ill before arriving to the Summit
  • Some respondents said they were sick, but their symptoms did not fall into the case’s outbreak definition (ie. they did not report diarrhea or vomiting)
  • Some respondents either did not finish the survey, or did not provide sufficient information
  • The survey link was compromised, meaning the survey was available to individuals who may not have attended the Summit

The survey uncovered lots of detail regarding the symptoms most attendees experienced:

  • 98 percent had diarrhea
  • 75 percent had stomach cramps
  • 44.9 percent had nausea
  • 33.8 percent had headaches
  • 24.1 percent had chills

Over half of the sick attendees fell ill during the mid to late hours of April 9 through the early hours of April 10. This finding lead investigators to believe that these victims were likely exposed at the same time and in the same location.

Narrowing Down the Origin of Contamination
Based on survey results, officials came to a number of conclusions. Sickened individuals were five times more likely to be apart of the outbreak if they experienced or engaged in any of the following:

  • Became ill in the days following the Summit, specifically with symptoms of diarrhea and/or vomiting
  • Attended Summit sessions on April 8 and 9
  • Ate lunch on-site on April 9, specifically the buffet-style chicken marsala served by the event caterer

Investigating the Event Caterer
On April 10, the caterer was notified of the possibility of an outbreak. Shortly thereafter, the Baltimore Health Department paid a visit to the catering facility.

Environmental findings: Officials identified and tested two ill foodservice workers. They also reviewed hot-holding and buffet service procedures. Written procedures were also reviewed and were found to be acceptable.

Lab findings: Also tested were 22 clinical specimens from the ill foodservice workers. Two workers tested negative for the pathogens tested while two ill attendees tested positive for Norovirus genogroup II.

Yes, an outbreak did occur. Based on lab testing, the likely etiology for most cases was C. perfringens. There were other illnesses, but they did not appear to be related to the majority of cases in this outbreak.

The outbreak was likely caused by the chicken marsala served at lunch on April 9. However, the Maryland DHMH maintains that they “don’t know exactly what happened.”

There were plenty of limitations throughout the investigation. Officials were not able to conduct food testing in real time. Food testing took place on April 16--exactly one full week after exposure is believed to have occurred. Food samples tested could have been from the same manufacturers and lots, but there were not the same exact foods served at the event. Also, there could have also been memory lapses in what attendees ate and exactly when they began to experience symptoms of illness. Finally, there were a number victims who decided not to provide stool samples because they were no longer ill.


  • Caterers and foodservice providers are urged to take precautions to avoid a similar outbreak from occurring again:
  • Ensure that internal food temperatures are measured appropriately and are representative
  • Detailed temperature logs should be updated as frequently as possible
  • Have a plan and adhere to it when corrective action needs to be taken when food temperatures measure less than the critical limit
  • Facilitate early recognition and investigation of outbreaks
  • Required reporters should immediately report suspected outbreaks to their local health department. The general public--those who do not work in health, foodservice or food safety--should still report suspected outbreaks to local officials.

This year's Food Safety Summit employed a different vendor and ultimately resulted in no reported cases of foodborne illness. Next May, the Summit will be held in Chicago, IL.

Tiffany Maberry is the digital editor for Food Safety Magazine.