The state of Maryland has only experienced four foodborne illness outbreaks in the past 10 years that sickened 100 people or more. Unfortunately for food safety experts, one of those outbreaks occurred at last year’s Food Safety Summit, an annual conference dedicated to food safety solutions. Last year’s conference in Baltimore ended with 216 of the 1,300 attendees sickened, predominantly with diarrhea, and some with nausea and vomiting. An investigation by the Maryland Department of Health and Mental Hygiene eventually found the smoking gun to be a chicken marsala dish, most likely contaminated with Clostridium perfringens, which was served at lunch on the second-to-last day of the conference. 17th-annual Food Safety Summit returned to Baltimore this year, and it made for a fitting forum to discuss lessons learned from last year’s ironic outbreak. At a session on Wednesday, attendees listened to a detailed outline of last year’s outbreak investigation as described by Alvina Chu, chief of the state health department’s Division of Outbreak Investigations. The outbreak was first reported by four attendees who fell ill in the wee hours of April 10 — the final day of the summit — after attending conference sessions the day before. As more reports came in, investigators quickly understood that the agent was not Norovirus, the most common cause of outbreaks at conferences. Most attendees were experiencing diarrhea, but not vomiting, a common symptom in Norovirus outbreaks. State health officials launched their investigation on April 16. Analyzing more than 200 reports, it was soon apparent that the illness onset times created a very tight epidemic curve, suggesting that almost all the cases were exposed at the exact same time and in the same location. The most likely timing for exposure was determined to be lunchtime on April 9. After submitting questionnaires to case patients and other attendees, the health department concluded that sickened attendees were five times more likely to have eaten a chicken marsala dish compared to those who didn’t get sick. However, approximately 30 percent of the sickened attendees did not eat the chicken marsala dish. Some attendees reported feeling sick before arriving at the conference, Chu said, so it was possible that they exposed others to illness regardless of the lunch served on April 9. “Please, if you know you’re sick and you’re planning to attend a conference, don’t go to the conference,” Chu joked to the audience. A few challenges plagued the investigation, she said, namely the late start to the investigation, which didn’t occur until a week after the time of exposure. Investigators were unable to test any of the food served that day, for example. Another problem was that not enough attendees reported their illness symptoms fast enough before they were tracked down. People who are feeling sick should always consider notifying the health department, even if it doesn’t feel urgent, Chu said. “Even if you don’t think it’s a problem, let us help figure out if it’s a problem,” she added. Finally, another challenge was getting enough attendees to volunteer stool samples. By the time the investigation was rolling, many attendees were feeling better and perhaps didn’t see the benefit of providing a stool sample. To that, Chu had one final, simple plea: “If you’re involved in a foodborne outbreak and someone asks you for a stool sample, please help us out and send us some stool,” she said. “You’re not really using it anyway.”