After an outbreak of paralytic shellfish poisoning that has sickened about 20 people, the Oregon Health Authority is urging people to discard mussels harvested from a stretch of the coast since Saturday.

All of the people involved reported recreationally harvesting mussels between Saturday and Sunday at Short Beach near Oceanside in Tillamook County, Hug Point near Arch Cape and near Seaside in Clatsop County. Some people have been hospitalized, but no deaths have been reported.

Paralytic shellfish poisoning is a foodborne illness caused by consuming contaminated shellfish. Symptoms usually set in within 30 to 60 minutes of eating the contaminated shellfish, and can include numbness of the mouth and lips, nausea, vomiting, diarrhea, weakness and in severe cases, shortness of breath or irregular heartbeat.

Health authority officials recommend people experiencing these symptoms immediately contact a health care provider and seek advice at the Oregon Poison Center at 800-222-1222.

On May 23, the Oregon Department of Fish and Wildlife and the Oregon Department of Agriculture closed mussel harvesting from Seal Rock State Recreation Site north to Cape Lookout due to high levels of the biotoxin. The closure was extended along the North Coast to the Washington state border on Sunday.

“We have two messages: If you have any mussels gathered since Saturday from beaches within the area of coastline that ODFW and ODA closed to harvesting — that you are preparing for a meal or keeping in the freezer for a later time — throw them out now and do not feed them to pets,” Emilio DeBess, epidemiologist in the state’s acute and communicable disease prevention section, said in a statement. “And if you have eaten any of these mussels and are feeling ill, see a doctor right away.”

DeBess added the recommendations only apply to mussels harvested by private individuals, not those harvested commercially and purchased in a grocery store or at a restaurant.

Paralytic shellfish poisoning can be deadly, especially to children. The illness can be prevented by avoiding potentially contaminated shellfish. Marine shellfish toxins cannot be destroyed by cooking or freezing, and shellfish that carry them do not necessarily taste different from uncontaminated shellfish. There is no antidote to paralytic shellfish poisoning, but treatment involves supportive care and, if necessary, respiratory support.