Gastrointestinal Illness Outbreak Tied to Raw Oysters


Consumption of oysters from a Mexican estuary has led to infections caused by multiple pathogens, with some individuals infected by more than 1 bug.

The US Centers for Disease Control and Prevention (CDC) is reminding the public of the dangers associated with raw or undercooked oysters in the wake of an outbreak of gastrointestinal illnesses linked to the shellfish.

The agency is working alongside public health officials in several states to investigate this outbreak, which has a suspected link to raw oysters harvested from an estuary in Mexico. Thus far, 16 cases have been reported across 5 states, with 2 documented hospitalizations. The ill range in age from 26 to 80 years with a median age of 38 years. It is reported that 67% of the ill are female.

In interviews with 15 of the ill individuals about consumptions and exposures prior to illness, all 15 people reported consumption of raw oysters from various restaurants in California and Nevada.

The onset of illness ranges from December 16, 2018, to April 4, 2019, and laboratory testing has revealed that infections have been caused by multiple pathogens, with some individuals infected with more than 1 pathogen.

The case counts by pathogen and/or illness include: 3 cases of Shigella fleneri, 3 cases of Vibrio parahaemolyticus, 1 case of Vibrio parahaemolyticus and Shiga toxin-producing E coli non-O157 coinfection, 1 case of Vibrio parahaemolyticus and Shigella flexneri coinfection, 1 case of Shigella flexneri and Campylobacter lari coinfection, 1 case of Vibrio albensis, 1 case of norovirus genogroup 1 infection, 1 case of infection of Vibrio with unknown species, and 4 cases of an illness with an unidentified pathogen.

Epidemiologic traceback has determined that the likely source of the outbreak is raw oysters that were harvested at Estero El Cardon in Baja California Sur, Mexico. The health officials have determined that 15 of the ill individuals consumed raw oysters from this estuary.

On May 6, 2019, a recall was issued by DiCarlo Seafood and publicized by the California Department of Public Health for raw oysters from Estero El Cardon. The following day, the US Food and Drug Administration (FDA) announced that the growing area that has been implicated in the outbreak has been closed and will remain closed while the area is investigated by the Mexican Shellfish Authorities.

According to the FDA’s statement, the last known harvest of products associated with the gastrointestinal illnesses occurred on March 2, 2019, and at this time it is believed that the contaminated products are no longer on the market.

However, due to a lag in the reporting timeline for gastrointestinal illnesses, state and federal officials are continuing to investigate potential cases linked to this outbreak. Illnesses may not be included in the current case counts, as the reporting process takes approximately 4 weeks.

The CDC reminds the public that any raw oysters, not just the oysters linked to this outbreak, can contain harmful germs that can lead to illness; therefore, all oysters and shellfish should be cooked thoroughly and individuals who prepare or handle raw shellfish should always wash their hands.

This is an ongoing outbreak investigation and updates will be provided when information becomes available.

For the most recent case counts in the gastrointestinal illness outbreak linked to raw oysters, check out the Contagion® Outbreak Monitor.

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