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Seafood Norovirus Outbreak in California

Posted in Food Safety,Our Blog,Outbreaks & Recalls on July 1, 2024

This year has been a bad year for shellfish. It seems like every time you click a homepage, there is another seafood norovirus outbreak in California linked to oysters.

Seafood Norovirus Outbreak in California Linked to Oysters from Mexico

In January 2024, cases of norovirus began popping up. Initially, 41 probable and confirmed cases were connected to the Fish Shop chain restaurant and Carlsbad Aquafarm. Shortly after, that case count rose to 69. Though 20 included those consuming oysters from other food venues.

The common food?


Specifically, oysters imported from locations in Mexico.

California Department of Health and U.S. Food and Drug Administration Investigates Outbreak

Both the California Department of Health and U.S. Food and Drug Administration (FDA) launched an investigation into the norovirus outbreak.

The source was tracked down to Baja California, Mexico. Laguna De Guerrero Negro and Laguna Manuela harvesting locations were implicated. An additional advisory included Sonora oysters from the Estero Morua harvest location.

As the number of harvest locations potentially contributing to the norovirus outbreak continued to rise, County Public Health began recommending against consuming all oysters imported from Mexico.

“The County recommends that people ask where oysters were harvested when eating out or getting food from wholesale locations to avoid consuming oysters imported from Mexico,” said Dr. Ankita Kadakia, Deputy County Public Health Officer. “Norovirus is typically a mild illness but can cause dehydration especially for the very young and very old. Given the increasing number of cases, the chance for others at greater risk for more severe illness in the same home is also increased. I want to remind people who become ill, and those that live with them, to wash their hands frequently to avoid contaminating surfaces and foods that could further spread the infection.” 

Norovirus Is Not the Only Concern

This seafood norovirus outbreak in California is not the only pathogen on the radar when it comes to oysters.

Consuming raw oysters exposes you to many different harmful bacteria, the toxins they produce, and viruses. In addition to norovirus, Vibrio, Shigella, and E. coli are commonly associated with consuming raw oysters.

Another Seafood Norovirus Outbreak in California

Not long after, another seafood norovirus outbreak in California was traced back to oysters.

San Diego County Public Health officials linked at least 11 confirmed and probable norovirus cases to frozen oysters imported from South Korea. At least one person was sent to the emergency room following a meal from 100s Seafood Grill Buffet in Mission Valley.

Cases were linked to the restaurant between March 31 and April 1.

Restaurant owners were cautioned to check their freezers for implicated frozen, raw half-shell oysters that could be labeled as “Amazing Sea Brand” or JBR (KR 15 SP).

Oysters are Filter Feeders

Oysters are filter feeders. They take in water, pull out the small bits of food they consume, and release the rest. A mature oyster can filter 50 gallons of water in a single day.

In addition to the bits of food and sea water, bacteria, viruses, and other pathogens also move through these shelled creatures. As a result, these pathogens can build up in their bodies.

When consumed raw, those pathogens can infect an unknowing consumer.

Infected oysters do not normally look, taste, or smell any different from those safe to eat. You really cannot tell without specialized laboratory tests.

Certain times of the year, algal and bacterial counts rise, making them more likely to be contaminated. This is the source of the phrase, “only eat oysters in months with R.” Meaning September through April. However, oysters harvested in any month of the year may be contaminated. The previous two norovirus outbreaks, for example, took place during prime “R” month periods.

What is Norovirus and How Bad Is It?

Norovirus is a highly contagious virus that causes vomiting and diarrhea. It is sometimes referred to as the “stomach flu” or a “stomach bug” though it is in no way related to the influenza virus. It is the leading cause of vomiting, diarrhea, and foodborne illness in the United States.

Everyone is susceptible to it. Young, old, and in between.

Symptoms of diarrhea, vomiting, nausea, and stomach pain may begin as early as 12 to 48 hours after exposure. Other symptoms may include fever, headache, and body aches.

Dehydration is a huge problem with illnesses that cause vomiting and diarrhea. When you lose more liquids than you can consume, it can cause significant health impacts.

Dehydration symptoms to look out for include:

  • Decreased urination
  • Dry mouth and throat
  • Dizziness when standing
  • Crying with few or no tears
  • Unusual sleepiness or fussiness

Most people with norovirus infection will begin feeling better within three days. However, they can continue to spread the virus for several more days.

The Gift That Keeps on Giving

Due to the extreme contagiousness of norovirus, it is important to help prevent further spread of the illness. A person contracting norovirus from consuming raw oysters can spread the sickness to others that they come in contact with.

Handwashing is important to control norovirus infections.

Wash your hands after you use the bathroom, help someone in the bathroom, or change a diaper.

A person with norovirus should not prepare food for others while they are infectious.

Other Shellfish Concerns in the News

June has been a fairly active month for shellfish in the news. There are currently two active shellfish advisories in the United States.

Alert on Certain Oysters from British Columbia, Canada

The FDA issued an alert in June instructing restaurants and retailers not to serve or sell and consumers not to eat certain oysters from British Columbia, Canada.

This alert was issued after the Canadian Food Inspection Agency (CFIA) alerted the FDA that recent monitoring activities detected elevated levels of paralytic shellfish toxins in certain harvesting locations.

Live oysters from Dailyfresh Shellfish, Inc were harvested from the Subarea 23-10 implicated in the announcement. Lot # 240531JM shipped to distributors in California were impacted. This product may have been further distributed to other states.

Alert on Certain Oysters from Oregon and Washington

The FDA issued another alert in June instructing restaurants and retailers not to serve and consumers not to eat certain shellfish from Oregon and Washington.

The Oregon Department of Agriculture alerted the FDA that certain oysters and bay clams due to elevated paralytic shellfish toxin levels in Netarts Bay and Tillamook Bay in Oregon on May 28, 2024. These products were distributed to the states of Oregon and New York and may have been further distributed to other states.

On the same day, the Washington State Department of Health alerted the FDA of a similar issue. All shellfish species harvested from Willapa Bay, certain dates from Stony Point, certain dates from Bay Center, and certain dates from Bruceport tested for elevated levels of paralytic shellfish toxin. These were distributed to the states of Arizona, California, Colorado, Hawaii, Nevada, Oregan, and Washington and may have been further distributed to other states.

Does This Mean Avoid All Shellfish?

With the significant risk associated with filter feeding shellfish, you may be thinking of casting those morsels aside forever. Should you avoid all shellfish?

Fortunately, that isn’t necessary.

However, raw shellfish should be avoided. Grilled, steamed, baked, barbeque. How ever you like it. Just be sure to cook it to the USDA recommended 145° F internal temperature measured with a food thermometer.

Stay in Touch with Make Food Safe!

If you’d like to know more about food safety topics in the news, like Seafood Norovirus Outbreak in California, check out the Make Food Safe Blog. We regularly update trending topics, foodborne infections in the news, recalls, and more! Stay tuned for quality information to help keep your family safe, while The Lange Law Firm, PLLC strives to Make Food Safe!

By: Heather Van Tassell (contributing writer, non-lawyer)