On Jan. 18 the Chattanooga-Hamilton County Health Department began investigating complaints of gastrointestinal illness associated with individuals who ate oysters at a local restaurant. Three unassociated groups of people who ate oysters at The Boathouse Rotisserie and Raw Bar (located at 1011 Riverside Dr.) became ill. A total of 19 people reported illness after eating at the restaurant between Monday, Jan. 12, and Sunday, Jan. 18, and developed symptoms such as nausea, vomiting and diarrhea 12-40 hours after eating. The majority of those ill reported eating raw oysters.

Following standard protocol, the Health Department conducted an investigation to determine the cause of the illness. The establishment fully cooperated with the Health Department’s procedures. Inspection of the restaurant along with interviews with and testing of foodhandlers at The Boathouse Rotisserie and Raw Bar did not implicate those persons or the restaurant as a source of infection.

Seventy-five percent of those tested were positive for norovirus. Confirmed by the Food and Drug Administration, the illnesses have been linked to raw shell oysters harvested off of the coast of Mississippi. Under advisement of the FDA, the Mississippi Department of Marine Resources is advising consumers not to eat oysters harvested from Conditionally Approved Area 2 “C” Shellfish Growing Waters in Mississippi from Jan. 5-9. These oysters may be contaminated with norovirus.

Oysters from this harvest area were also served at Easy Bistro and Bar (located at 203 Broad St.) and Blue Orleans Creole Restaurant (located at 3208 Amnicola Highway), but no associated illnesses have been reported to the Health Department. There have been no further reports of illness associated with this outbreak. Affected oysters are no longer being served in the Chattanooga area.

Consumers who ate raw oysters on or after Jan. 5, and are concerned about the origin of oysters they have recently purchased should contact the place of purchase to determine if the oysters were harvested from the identified area during the Jan. 5-9 period. Individuals who are concerned that they may have become ill as a result of consuming oysters should contact their medical provider and the Chattanooga-Hamilton County Health Department.

Oysters cultivated in coastal areas close to human activities can be contaminated by human sewage, which can spread different types of viruses, including noroviruses.

Noroviruses are a group of viruses that are the most frequent cause of gastrointestinal illness outbreaks. The symptoms of norovirus illness usually include nausea, vomiting, diarrhea, and some stomach cramping. Sometimes people have a low-grade fever, chills, headache, muscle aches, and a general sense of tiredness. Most people show symptoms within 48 hours of exposure to the virus. The illness is self-limiting and usually subsides within one to two days, most often without serious complications.

The Health Department recommends that persons should avoid raw oyster consumption regardless of where the oysters are harvested. Persons with weakened immune systems, including those affected by AIDS, and persons with chronic alcohol abuse, liver, stomach or blood disorders, cancer, diabetes or kidney disease are more susceptible to complications from infections with diseases associated with eating raw oysters.

“It is always best to cook oysters thoroughly,” says Margaret Zylstra, epidemiologist manager at the Chattanooga-Hamilton County Health Department. “Doing so will minimize the risk of foodborne illness.”

Consumers can continue to enjoy oysters in many cooked preparations by following this advice:

At Restaurants and other Foodservice Establishments:
• Order oysters fully cooked.

In the Shell:
• Purchase oysters with the shells closed. Throw away any oysters with shells already opened.
• To prepare oysters for eating, choose one of the following methods:
Boil oysters until the shells open. Once open, boil for an additional 3-5 minutes.
Steamer - add oysters to water that is already steaming and cook live oysters until the shells open; once open steam for another 4-9 minutes.
• Use smaller pots to boil or steam oysters. Using larger pots, or cooking too many oysters at one time, may cause uneven heat distribution, which may cause the oysters in the middle to not get fully cooked.
• Discard any oysters that do not open during cooking.

Shucked Oysters:
To prepare oysters for eating, choose one of the following methods:
• Boil or simmer shucked oysters for at least 3 minutes or until the edges curl.
• Fry at 375 degrees for at least 3 minutes.
• Broil 3 inches from heat for 3 minutes.
• Bake at 450 degrees for 10 minutes.

For more information, call the FDA Food Safety Hotline at 1-888-SAFEFOOD or the Chattanooga-Hamilton County Health Department at (423) 209-8190