SACRAMENTO (CBS13) – We are now being warned not to eat raw oysters harvested from south and central Baynes Sound, in British Columbia, Canada.

The California Department of Public Health reports about 100 people have tested positive for Norovirus. All report eating raw oysters they bought at restaurants or retailers.

The illnesses are all traced back to four farms in British Columbia. Those farms were closed between March 23 and April 13 and haven’t reopened.

Restaurants and retailers are being told to not distribute, serve or sell oysters coming from this region. The oysters have the following landfile numbers on the shellfish tags: CLF #1402060, CLF #1411206, CLF #1400483, and CLF #278757.

If you’ve eaten raw oysters, the CA Dept. of Public Health advises you to visit your doctor if you become ill. The CDPH Director and State Public Health Officer, Dr. Karen Smith, also reminds people to: “avoid eating raw and undercooked shellfish, including oysters, to reduce your risk of illness. 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.”

Norovirus quickly spreads from person-to-person. Symptoms, including vomiting, diarrhea, nausea and stomach cramps, usually begin 12-48 hours after a person comes in contact with the virus.