The Prevalence of Salmonella in Food and Elsewhere
Most Salmonella infections are caused by contaminated food, especially food from animal origins—like poultry and ground beef.
Most Salmonella infections are caused by eating contaminated food, especially food from animal origins.  One study found that 87% of all confirmed cases of Salmonella were foodborne, with 10 percent from person-to-person infection and 3% caused by pets.  As explained in a comprehensive report issued by the USDA’s Economic Research Service:
Salmonella contamination occurs in a wide range of animal and plant products (table 3). Poultry products and eggs are frequently contaminated with S. Enteritidis, while beef products are commonly contaminated with S. typhimurium. Other food sources of Salmonella may include raw milk or other dairy products and pork. Salmonella outbreaks also have been traced to contaminated vegetables, fruits, and marijuana.
Another study went into even greater detail in explaining the prevalence of Salmonella and the sources of human infection, stating as follows:
A food item was implicated in 389 (46%) outbreaks of S. Enteritidis infection from 1985 through1999; in 86 (22%) of these, more than one food item was implicated. Of the 371 outbreaks for which information was available, 298 (80%) were egg associated. This proportion ranged from 10 (71%) of 14 in 1985 to 19 (95%) of 20 in 1997. Of outbreaks caused by a single vehicle for which information was known, 243 (83%) of 294 were egg-associated, as were 55 (71%) of 77 outbreaks in which more than one food item was implicated.
Among single foods implicated in egg-associated outbreaks, 67 (28%) of 243 were foods that contained raw eggs (e.g., homemade ice cream, Caesar salad dressing, tiramisu, egg nog). Sixty-five (27%) of the outbreaks implicated traditional egg dishes such as omelets, French toast, pancakes, and foods that use egg batter, such as crab cakes, chile rellenos, egg rolls, and Monte Cristo sandwiches. Sixty-three (26%) outbreaks implicated dishes known to contain eggs, such as lasagna, ziti, and stuffing, which would have been expected to have been fully cooked but probably did not reach temperatures sufficient to kill S. Enteritidis. Thirty-six (15%) outbreaks implicated egg dishes that were “lightly cooked” (e.g., hollandaise sauce, meringue, cream pies). The food vehicles in 12 (5%) outbreaks were reported to contain eggs but could not be classified because information on how the dishes were prepared was not provided.
Seventy-three (20%) of the 371 confirmed outbreaks for which information was provided involved vehicles that did not contain eggs. Twenty (27%) of these outbreaks were associated with poultry (chicken or turkey), 8 (11%) with beef, and 6 (8%) with foods containing shrimp (3 outbreaks), bologna (1), pork (1), and pepper loaf (1). Other implicated foods included potatoes (3), beans (3), desserts (3), salad (3), macaroni and cheese (1), cheese sauce (1), goat cheese (1), chili (1), and a pureed diet (1). In 22 (30%) of the non–egg-associated outbreaks, more than one food was implicated. In four of these outbreaks, cross-contamination with raw eggs was suspected.