The Coastal Post - September 2000

State Health Director Warns Public About Eating Raw Oysters

SACRAMENTO: Citing recent illnesses associated with the consumption of raw or undercooked oysters, State Health Director Diana Bont, RN, Ph.D., today urged consumers not to eat oysters unless they have been thoroughly cooked. Individuals with weakened immune systems, liver diseases, diabetes or other chronic illness or who are taking daily doses of stomach antacid are especially susceptible to illness from eating raw or undercooked oysters.

Three San Francisco residents and a resident of Sonoma County have become ill since May with Vibrio parahaemolyticus, a natural marine bacteria common during periods of warm weather, after consuming raw oysters harvested from Tomales Bay in Marin County. The individuals, all males ranging in age from 29 to 60, have recovered.

Vibrio parahaemolyticus infections can cause diarrhea, abdominal cramps, nausea, vomiting, headache, fever and chills. The onset of symptoms is usually 12 to 24 hours after eating. Most illnesses clear up after two to four days. This illness is rarely fatal, but severe cases may require antibiotic treatment and hospitalization.

Since 1997, four multi-stage outbreaks of Vibrio parahaemolyticus infection in the United States involved raw or undercooked oysters harvested from the Pacific Coast, the Gulf Coast and Long Island Sound in New York. In 1998, more than 100 confirmed illnesses resulted from the raw and undercooked consumption of oysters harvested in British Columbia and the state of Washington. Many of the individuals who became ill lived in the San Francisco Bay area, but illnesses also were reported in Los Angeles, Sacramento and San Diego.

Warm summer temperatures can increase the number of Vibrio parahaemolyticus organisms in shellfish to levels that cause disease. Inadequate refrigeration after harvest, during transport, storage and display can greatly increase the risk of illness by allowing Vibrio parahaemolyticus organisms to multiply. Bont also advised that prior to consumption, all shellfish, especially oysters, mussels and clams, be kept refrigerated to prevent the growth of any existing Vibrio parahaemolyticus bacteria.

Cooking can be very effective in killing the Vibrio parahaemolyticus bacteria. However, oysters that are steamed, barbecued or served "Rockefeller-style" may be undercooked. To ensure safety, Bont advised that the internal temperature of the oysters needs to reach at least 145 degrees to kill the Vibrio parahaemolyticus bacteria. Preparations such as marinating oysters in lemon juice, vinegar, cocktail sauce or other ingredients are not a substitute for cooking and do not provide adequate protection.

Bont further advised consumers who wish to reduce their general risk of food-borne illness to avoid eating raw or lightly cooked foods of animal origin, including beef, eggs, fish, lamb, poultry and shellfish. Thorough cooking is the best way consumers have to eliminate bacteria from these products.

Coastal Post Home Page