August 4, 2006 - (SACRAMENTO) - A recent increase in the number of illnesses linked to the consumption of raw oysters from Washington state has prompted State Public Health Officer Dr. Mark Horton to remind Californians to thoroughly cook raw oysters before eating them in order to reduce risk of illness. 

"It is best to thoroughly cook raw oysters no matter where they are from or the time of year they are harvested," said Horton.  "The potential for developing a food-borne illness is always high when handling or eating raw shellfish."

Approximately 70 illnesses caused from eating raw Washington state oysters have been reported in several states, including 24 in California.  The Washington state Department of Health issued recalls on products harvested since July 13 and July 20 from various parts of the state. 

The recalled products were distributed throughout California.  Twenty-four confirmed or suspected cases have been reported in the following seven California counties:  Los Angeles, 3; Marin, 2; Monterey, 2; San Diego, 2; San Francisco, 4; San Mateo, 5; Santa Barbara, 2; Santa Clara, 1; and Ventura, 3.

The illnesses were caused by a naturally occurring bacterium that affects oysters called Vibrio parahaemolyticus.  This bacterium is common to saltwater environments throughout the United States.  Generally, the level of this pathogen is low in the ocean, but it can increase when water temperatures rise during the summer months.  Inadequate refrigeration following harvest, transport and storage may also allow the bacteria to multiply to levels that may cause illness when oysters are eaten raw. 

Lightly cooked oysters, including steamed oysters, Oysters Rockefeller or marinated oysters as used in ceviche, are also a risk.  The California Department of Health Services (CDHS) recommends that oysters be cooked to a minimum internal temperature of 145 degrees (boiled until the shells open and an additional three to five minutes thereafter) to destroy the bacteria.

In addition, illnesses have been linked to other seafood, including sushi and ceviche, that have been consumed raw or undercooked.  Vibrio parahaemolyticus illnesses can also occur when consumers inadequately refrigerate food after purchase or when food is cross contaminated in the kitchen by contact with raw seafood or raw shellfish products.

Vibrio parahaemolyticus infections can cause diarrhea, abdominal cramps, headache, fever and chills.  Symptoms generally begin one day after eating contaminated foods.  Most individuals recover without treatment within several days.  Severe cases may require medical treatment, but infections are rarely fatal.  Individuals who are at high risk of severe illness include those with chronic liver disease, cancer, AIDS or other conditions that weaken or compromise the immune system. 

Anyone who has recently eaten raw oysters and is experiencing the symptoms mentioned above should contact their physician.  Consumers and retailers should contact the place of purchase or supplier if they have any questions about the source of oysters and whether they are part of the recall.

For additional information, contact CDHS at (916) 650-6500 or 1-800-495-3232 or the Washington state Department of Health at 1-360-236-3330 or www.doh.wa.gov/ehp/sf/biotoxin.htm.

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