Confirmation that shellfish from Samish Bay in northwest Washington state was the source of at least one illness, and possibly three others, caused by the bacterium Vibrio parahaemolyticus, has prompted the state’s health department to close commercial oyster harvesting in the bay until Sept. 30.

According to the Centers of Disease Control and Prevention, Vibrio parahaemolyticus is a bacterium in the same family as those that cause cholera and Vibrio vulnificus. It lives in brackish saltwater and causes gastrointestinal illness in humans. V. parahaemolyticus naturally inhabits coastal waters in the United States and Canada and is present in higher concentrations during summer. It is a halophilic, or salt-requiring, organism.

Taylor Shellfish Farms, which has one of its facilities on Samish Bay, will be bringing oysters from its other shellfish farms to its store on Samish Bay so it can continue selling oysters to customers in that location.

In the meantime, clam, mussel and geoduck harvest will continue at the farm.

A smaller oyster farm on the bay, Blau Oyster Co., is hoping to obtain an exemption from the state that will allow it to sell shucked oysters with labels warning customers to cook the oysters.

Bill Dewey told the Skagit Valley Herald that the low tides and hot sunny weather boost the potential for the Vibrio bacteria to proliferate. He warned that, just to be safe, recreational harvesters should cook the oysters they harvest during this hot weather. For more information about shellfish closures in Washington state, as well as maps showing which beaches are closed, go here.