In June 2013 local and state public health staff in Massachusetts investigated a cluster of gastrointestinal illnesses among persons who attended a wedding held on June 15, 2013 in Orleans, Massachusetts. A Needham resident notified the Food Protection Program (FPP) at the Massachusetts Department of Public Health (MDPH) that guests at his son’s wedding were ill with vomiting and diarrhea in the days following the ceremony. Several of the ill guests also attended a rehearsal dinner on Friday, June 14 at the Wayside Inn located in Chatham, Massachusetts.

Staff from the MDPH Division of Epidemiology and Immunization (EPI) program asked wedding attendees to complete a survey about wedding activities and food consumption. Case patients were defined as any guest who reported gastrointestinal symptoms within 48 hours of the rehearsal dinner or the wedding. Fifty four out of 133 (41%) wedding attendees completed the survey. Twenty five (46%) respondents reported illness with symptom onset between June 15 and June 21. Based on survey data, investigators determined that illness was linked to attending the rehearsal dinner and not the wedding ceremony or events held afterwards. Analysis of food items consumed at the rehearsal dinner revealed that consumption of raw oysters was the only food item statistically associated with illness. Persons who consumed raw oysters were 10 times more likely to become ill than persons who did not consume raw oysters. Four ill guests who attended the rehearsal dinner submitted stool specimens to the MDPH state public health laboratory for testing. Tests showed that all four were infected with norovirus and that all matched by genotype analysis (G1.4). All stool specimens were negative for other foodborne pathogens.

On June 18 an inspector from MDPH FPP collected samples of leftover food that had been served at Wayside Inn rehearsal dinner. The food samples were walnuts, M&M candy, ice cream, chocolate chips and raw oysters. Oysters collected for testing by MDPH FPP were tagged as being harvested on June 6 from area MA-SC:61. The oysters were positive for norovirus G1.4 and matched the strain found in stool specimens collected from ill wedding attendees. A review of Wayside Inn invoices and oyster handling at the Wayside Inn revealed that co-mingling of oysters was likely and that the contaminated oysters could have also been harvested from area MA-SC:49. Oysters served at the rehearsal dinner were purchased from Chatham Fish & Lobster, a wholesale seafood distributor in Chatham, Massachusetts.

The norovirus outbreak among dinner guests at the Wayside Inn coincided with reports of gastrointestinal illnesses in patrons who consumed raw oysters at two other area restaurants. Six persons among a group of 35 guests who attended a birthday dinner at The Port, a restaurant located in Harwich, Massachusetts became ill within 48 hours following the June 15 dinner. Analysis of food items consumed at the party revealed that consumption of raw oysters was significantly associated with illness (Relative Risk 5.83, 95% Confidence Intervals 0.92, 37.08). Four ill employees at The Port submitted stool samples that tested positive for norovirus G1.4. Investigators determined that raw oysters served at the birthday event were purchased from Chatham Shellfish Company, a wholesale seafood distributor located in Chatham. The oysters were harvested on June 13 from area MA-SC:49. Persons who ate at Mattakeese Wharf, a restaurant located in Barnstable, Massachusetts, reported illness following consumption of raw oysters at the restaurant on June 17. Shellfish tags showed that oysters served at Mattakeese Wharf on that date were purchased from Chatham Fish and Lobster with a harvest date of June 13, 2013 and harvest area MA-SC:49. One oyster harvester also tested positive for norovirus G1 and was genotype G1.4. In response to the three outbreaks, the Massachusetts Division of Marine Fisheries closed shellfish harvest areas MA-SC:49, SC:50, and SC:51 on June 20, 2013.

Public health investigators concluded that guests at the Wayside Inn and other area restaurants were infected with norovirus G1.4 as a result of consuming raw oysters harvested from MA-SC:49. In an April 3, 2014 outbreak report MDPH investigators noted that “It is clear that these contaminated oysters led to the illnesses of the oyster harvester, the guests at the Wayside Inn, and the guests and food handlers at the Port Restaurant.”