What is the causative agent for diarrhea after consuming undercooked shellfish?

The causative agent for diarrhea after consuming undercooked shellfish is Vibrio vulnificus. This bacterium is commonly found in warm, coastal waters and can contaminate shellfish, particularly oysters. When these shellfish are consumed raw or undercooked, the bacteria can enter the human gastrointestinal tract, leading to gastrointestinal illness characterized by diarrhea.

Vibrio vulnificus infections can be particularly severe in individuals with certain risk factors, such as liver disease or weakened immune systems, and can cause additional complications beyond standard gastrointestinal symptoms. The ability of this pathogen to thrive in marine environments makes it a significant concern for public health, particularly during warmer months when water temperatures rise.

In contrast, Norovirus is more commonly associated with outbreaks linked to contaminated food or water and is not specifically tied to shellfish. Escherichia coli, while a well-known cause of foodborne illness, is more commonly associated with undercooked beef or contaminated produce, rather than shellfish. Campylobacter is also a recognized cause of gastroenteritis, often linked to poultry or contaminated water, rather than shellfish consumption. Thus, the link specifically between shellfish and Vibrio vulnificus is what identifies it as the correct causative agent in this scenario.