State health officials have extended to the Sonoma Coast recent warnings about the risks of consuming sport-caught mussels, clams, oysters, whole scallops and other bivalves in the wake of testing that has turned up evidence of naturally occurring paralytic shellfish poisoning in recent weeks.

The expanded notice comes as Marin County Public Health announced its first confirmed case of human illness, which occurred in a patient who ate mussels harvested Sunday at Dillon Beach, officials said Wednesday.

The unidentified patient had been hospitalized for neurological symptoms and is “getting better,” Marin County Public Health Director Matthew Willis said in a news release. “Fortunately, the clinician was aware of the elevated PSP (paralytic shellfish poisoning) levels in locally sport-harvested shellfish and made a timely diagnosis,” he said.

State health officials last week issued notices about the dangers of eating recreationally caught shellfish off the coast of San Mateo, San Francisco and Marin counties because of unhealthy levels of harmful toxins produced in phytoplankton blooms that tend to thrive in springtime conditions off the Northern California coast.

The warning does not apply to commercial produced bivalves, which are farmed in controlled settings and subject to routine testing.

Test levels in sample mussels harvested from the Chimney Rock sentinel station in the Point Reyes National Seashore returned paralytic shellfish poison levels 37 times the “alert” level, Marin County health officials said. The samples tested off Chimney Rock last week produced the highest levels in Marin County in 20 years, health officials said. The marine toxin can cause a host of neurological symptoms ranging from tingling around the mouth and fingertips minutes or hours after eating toxic shellfish, to a loss of balance, lack of muscular coordination, slurred speech and difficulty swallowing, Sonoma County health officials said.

In severe cases, patients may suffer complete muscular paralysis and death.

Cooking does not neutralize the toxin.

California has had 542 reported cases of sickness and 39 deaths attributed to the substance over the past 90 years, Marin County Public Health reported.

Sonoma County officials said the warnings were expected to last several weeks, until multiple clean tests confirmed the shellfish were again safe to consume.

For the most current information on shellfish advisories and quarantines, contact the California Department of Public Health at 800-553-4133 or at