DISCOVERY BAY — Seven vacationing family members were hospitalized, one so severely that she was placed on a ventilator, after eating mussels tainted with a potentially deadly marine biotoxin that they had harvested from Discovery Bay over the weekend, health officials said.

The woman placed on a ventilator Sunday was taken off it Monday but remained at Jefferson Healthcare Hospital in Port Townsend for observation.

Jefferson County Public Health said members of the Seattle-area family, who are not named, fell ill with paralytic shellfish poisoning, or PSP, after harvesting them Saturday.

The victims, aged 19 to 68, got sick several hours after eating the mussels from a beach that has been closed to recreational shellfish harvesting for high levels of PSP since mid-July.

“When symptoms worsened, 9-1-1 was called,” said Jefferson County Public Health Director Jean Baldwin.

The family was taken to Jefferson Healthcare early Sunday.

“Two members of the family were admitted to [Jefferson Healthcare], one requiring treatment on a mechanical ventilator,” Baldwin said.

“Two were transferred to Harrison Hospital (in Bremerton) in case their symptoms worsened and ventilator treatment would be needed,” she added.

“Three others were held for observations at Jefferson Healthcare.”

PSP can cause numbness and muscle paralysis from 15 minutes to 10 hours after the toxin is consumed.

Symptoms include a tingling of the lips and tongue, tingling of the hands and feet, difficulty speaking and difficulty breathing.

If left untreated, paralysis can lead to death.

In a follow-up interview, Baldwin said Monday that it is “pretty unusual” to have seven cases of PSP at one beach.

There are usually no more than seven cases of PSP in the entire state per year, she added.

“We’ve seen a few travelers get sick, but not all in one place, not all at one time,” Baldwin said.

PSP, also known as red tide, is caused by a naturally occurring biotoxin that is produced by microscopic algae.

Most beaches on the North Olympic Peninsula remain closed to recreational shellfish harvesting because of high levels of PSP toxin.

Warning signs have been posted at the affected beaches, including at Discovery Bay.

“I think it’s been over a decade since we’ve had a PSP case (on the North Olympic Peninsula), and then it was much milder than these,” said Dr. Tom Locke, public health officer for Clallam and Jefferson counties.

“It’s noteworthy in terms of the severity of the symptoms, and then, No. 2, the fairly large number of the cluster.”

A sample taken from a Discovery Bay shellfish two weeks ago showed 7,000 micrograms of PSP.

Health officials close beaches when the level reaches 80 micrograms.

Affected shellfish include mussels, clams, oysters, scallops and other molluscs.

It does not apply to shrimp or crab meat, but crab guts can contain unsafe levels and should be cleaned thoroughly.

Marine biotoxins are not destroyed by cooking or freezing.

Commercially harvested shellfish are tested for toxins prior to distribution and are considered safe to eat, the state Department of Health has said.

Peninsula beaches were closed this summer because of elevated levels of PSP, as well as the less-dangerous diarrhetic shellfish poisoning, or DSP.

Fisheries that remain closed for PSP are Discovery Bay, Admiralty Inlet, Port Townsend Bay, Kilisut Harbor, including Mystery Bay, Oak Bay, Mats Mats Bay and Port Ludlow south to the Hood Canal Bridge.

All Clallam County beaches remain closed for recreational shellfish harvesting for unsafe levels of PSP.

Before harvesting shellfish, check the state Department of Health website at http://tinyurl.com/7u33gob or phone the state biotoxin hotline at 800-562-5632.

Reporter Rob Ollikainen can be reached at 360-452-2345, ext. 5072, or at rollikainen@peninsuladailynews.com.