Again, that depends on how you look at the issue. Certain foods are especially dangerous for some people because of the likelihood that they contain a particular pathogen. For example, Listeria monocytogenes rarely causes illness in the general population, but if a pregnant woman becomes infected, the developing fetus also may become infected and may die. Foods that are safe for most people may be deadly for a small group of people. Some foods may be rarely contaminated, but the pathogen of concern may be especially virulent. For example, the incidence of Escherichia coli O157:H7 in raw ground beef is approximately 1%, so the risk the food will be contaminated is relatively low. However, only a few cells of E. coli O157:H7 are necessary to cause illness, so when a contaminated food is consumed without sufficient cooking, illness is more likely. In general, raw foods often present a higher risk of foodborne illness than properly cooked foods, because many pathogens are sensitive to heat.