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Why are raw shellfish a possible source of cholera infection?

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Diagram of a water treatment plant showing the process from water inlet through mixing, coagulation, flocculation, settling, filtering, chemical treatment with chlorine, storage, and high-lift pumping to the distribution system. — water purification Water from inlets located in the water supply, such as a lake, is sent to be mixed, coagulated, and flocculated and is then sent to the waterworks for purification by filtering and chemical treatment. After being treated, the water is pumped into water mains for storage or distribution.

Raw shellfish are a significant source of cholera infection because they are often harvested from water contaminated with the bacterium Vibrio cholerae.1

As filter feeders, shellfish can concentrate these bacteria within their tissues when living in environments affected by sewage or fecal contamination. Because the disease spreads via the fecal-oral route, consuming this seafood raw or undercooked allows the pathogen to enter the human digestive system directly. Once ingested, the bacteria colonize the intestine and secrete an enterotoxin that disrupts the body's ability to regulate water and electrolyte balance, leading to the severe symptoms associated with cholera.12

From a public health perspective, the risk is effectively mitigated by ensuring proper sanitation and thoroughly cooking all shellfish, which destroys the bacteria and prevents transmission.1