Fifty to 100 Americans die annually from a virulent form of E.coli bacteria found mostly in ground beef, according to a preliminary analysis of food poisoning data, an official with the U.S. Centers for Disease Control said Wednesday.The information is part of a CDC project now underway to calculate more accurately how many Americans are sickened and die each year

from contaminated hamburger, eggs, lettuce, milk and other foods. Dr. Patricia Griffin, chief of the CDC\\\'s food-borne diseases epidemiology section, cautioned that the numbers were tentative until a final report is completed in early 1999.