From what cuts of beef are ground beef and hamburger made? Generally, ground beef is made from the less tender and less popular cuts of beef. Trimmings from more tender cuts may also be used. Grinding tenderizes the meat and the fat reduces its dryness and improves flavor.
Can bacteria spread from one surface to another? Yes. It is called cross-contamination. Bacteria in raw meat juices can contaminate foods that have been cooked safely or raw foods that won't be cooked, such as salad ingredients. Bacteria also can be present on equipment, hands, and even in the air.
Is it dangerous to eat raw or undercooked ground beef? Yes. Raw and undercooked meat may contain harmful bacteria. USDA recommends not eating or tasting raw or undercooked ground beef. To be sure all bacteria are destroyed, cook meat loaf, meatballs, and hamburgers to a safe minimum internal temperature of 160 °F (71.1 °C). Use a food thermometer to check that they have reached a safe internal temperature.
http://www.fsis.usda.gov/Fact_Sheets/Ground_Beef_and_Food_Safety/index.asp#8