Seafoods carry about the same risk of bacterial infections and poisonings as other meats. The riskiest seafoods are raw or undercooked shellfish, particularly bivalves, which trap bacteria and viruses as they filter the water for food, and which we eat digestive tract and all, sometimes raw. As early as the 19th century, public health officials connected outbreaks of cholera and typhoid fever with shellfish from polluted waters. Government monitoring of water quality and regulation of shellfish harvest and sales have greatly reduced these problems in many countries. And scrupulous restaurant owners make sure to buy shellfish for the summer raw bar from monitored sources, or from less risky cold-water sources. But lovers of raw or lightly cooked seafood should be aware of the possibility of infection.