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Public health officials expand investigation into oyster-related illnesses

The San Diego County Administration Building is shown on Jan. 12, 2021.
Zoë Meyers
The San Diego County Administration Building is shown on Jan. 12, 2021.

San Diego County public health officials announced they are expanding an investigation into oyster-linked illnesses to include all oysters harvested from Mexico.

Health officials Thursday are recommending consumers and restaurants throw away any oysters imported from locations in Mexico until further notice.

According to the county Health and Human Services Agency, the local norovirus outbreak now includes 69 confirmed and probable cases. The severity of the infections in San Diego County has remained mild, with no hospitalizations reported to date. The initial investigations identified 41 probable and confirmed norovirus cases linked to oysters harvested in Sonora, Mexico. The sickened patrons dined at the Fish Shop chain and Carlsbad Aquafarm. Twenty-eight more cases have been added, including 20 who ate oysters from other food venues.


"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," Kadakia said. "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."

According to the county, oyster associated norovirus cases are also being reported in Orange, Riverside, San Bernardino, Ventura and Los Angeles counties. Both the California Department of Public Health and U.S. Food and Drug Administration are now actively engaged in the investigation.

The FDA, which has jurisdiction over oysters imported into the country, issued an initial advisory on Jan. 11, based, at least in part, on the findings of the investigation conducted by county health officials, a statement from the county read.

On Wednesday, the FDA then issued a second advisory for Laguna De Guerrero Negro and Laguna Manuela, both on the Pacific Coast of Baja California, Mexico but locations geographically distant from Sonora. Today, FDA updated the initial advisory on Sonora oysters to include a second harvest location, Estero Morua.


The new FDA recommendations advise restaurants and retailers to dispose of any oysters they still have or contact their distributor to coordinate return or destruction. People who have them in their homes should do the same.

"All of the implicated oysters were harvested in December 2023 and no oysters since then have been distributed to food venues in San Diego from those locations," the county statement reads.

If you eat raw or undercooked oysters, germs that might be in the oyster can make you sick.

People infected with norovirus generally develop nausea, vomiting, diarrhea, stomach cramps, fever and body aches 12 to 48 hours after consuming contaminated foods. The illness typically lasts for 1-3 days. The vomiting and diarrhea can lead to dehydration requiring medical attention, especially in young children, older adults and people with other illnesses.

HHSA is working with the California Department of Public Health, including the Shellfish Program, to continue investigating illnesses associated with oysters. To report illness to the County after dining out or purchasing from wholesale food locations call 858-505-6814, or email

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