Salmonella infections due to contaminated food products make many people ill each year and are responsible for substantial economic costs. Salmonella infections are potentially serious and may be fatal, particularly for the elderly and people with weak immune systems (see box on Salmonella infections). However, most salmonellosis cases do not result in a visit to a medical facility and are never reported to public health agencies. The high proportion of unreported cases makes it difficult to determine the true incidence of salmonellosis, and has resulted in a wide range of estimates of the annual economic costs of foodborne Salmonella infections. Many Salmonella infections are caused by undercooked shell eggs, which may be contaminated by hens infected by Salmonella serotype Enteritidis, one of the most common Salmonella strains. Effective August 1999, Federal regulations will require that shell eggs packed for retail sale to consumers be stored and transported at or below 45 degrees Fahrenheit to reduce the risk of Salmonella infections. USO A was unable to make a definitive estimate of the potential economic benefits of this rule, partly because of the uncertainty about the economic costs of Salmonella infections. USDA shares federal regulatory responsibility for egg safety with the Food and Drug Administration (FDA), which recently proposed requiring safe handling labels on egg cartons to warn consumers about the risk of illness associated with Salmonellacontaminated shell eggs. Previous estimates of the economic costs due to foodborne Salmonella infections by USDA's Economic Research Service (ERS) were based on the best available estimates of the annual number of infections and the associated medical expenses and productivity losses. New information about the incidence, severity, and medical consequences of salmonellosis has since become available from the Foodborne Diseases Active Surveillance Network (FoodNet) and other sources, allowing us to refine the previous estimates