SACRAMENTO, Calif. – The California Department of Public Health is warning residents to not eat raw or undercooked oysters from British Columbia, Canada, as they may be linked to an ongoing outbreak of norovirus.

According to officials with CDPH, at least 34 people in California fell ill between March 11 and March 19 after consuming oysters at restaurants across the state, with the oysters all hailing from British Columbia. The Canadian oysters have also been linked to norovirus cases in several other states, according to CDPH.

Norovirus is described by health officials as a “highly contagious virus” that can spread from person to person through surfaces or by consuming raw oysters. Symptoms- including nausea, vomiting, diarrhea, and stomach cramps- usually set in within 12 to 48 hours after contact and can last for one to three days.

“Avoid eating raw and undercooked shellfish, including oysters, to reduce your risk of illness,” said Dr. Tomás J. Aragón, CDPH Director and State Public Health Officer. “If you do eat shellfish, cook it until it reaches an internal temperature of at least 145°F. Quick steaming isn’t sufficient to kill norovirus.”

Restaurant owners and oyster buyers are encouraged to check their supplies to see if any are tagged with the following landfile numbers: CLF #278741, CLF #278757, CLF #278737, and CLF #1411206.

If you do become ill after eating oysters, CDPH officials recommend reaching out to your health care provider and your local health department to report the sickness.

For more information on norovirus, click here.