Salmonella is a rod-shaped, motile bacterium which is a cause of food poisoning. The bacteria is commonly found in poultry and swine. Other sources include insects, factory and kitchen surfaces, animal feces, raw meats and raw seafood.

Within 6-48 hours of contact with the salmonella bacterium, nausea, vomiting, abdominal cramps, diarrhea, fever, and headache may appear. Artritic symptoms may follow 3-4 weeks after the initial onset.

You should keep your cooking area clean, wash hands and utensils with hot, soapy water frequently, and cook food thoroughly. (I've never gotten sick eating sashimi. I wonder how they make sure to avoid salmonella.)

Source: The Bad Bug Book, by US FDA: