Norovirus, Salmonella Were Leading Causes of Foodborne Disease Outbreaks in 2006

Norovirus and Salmonella were the leading causes of foodborne disease outbreaks in 2006, according to a report released today by the Centers for Disease Control and Prevention (CDC). The report, based on investigations of foodborne disease outbreaks provides the most recent report of how many illnesses were linked to specific types of foods. 

There were 1,270 reported foodborne disease outbreaks in 2006, which resulted in 27,634 illnesses and 11 deaths, according to the surveillance report prepared by the agency’s OutbreakNet team. Among these 1,270 outbreaks, 621 had a confirmed single cause; the cause was most often norovirus (54 percent of outbreaks), followed by Salmonella (18 percent of outbreaks). The analysis was done on data from the 243 outbreaks in which a single food commodity was identified and reported to CDC.

Foodborne outbreaks of norovirus occur most often when infected food handlers do not wash their hands well after using the toilet; foodborne outbreaks of Salmonella occur most often when foods that have been contaminated with animal feces are eaten raw or insufficiently cooked.

The food commodities associated with the largest number of cases of illness in 2006 were poultry (21 percent of all outbreak-associated cases), leafy vegetables (17 percent), and fruits-nuts (16 percent). The food commodity categories defined by CDC are fish, crustaceans, mollusks, dairy, eggs, beef, game, pork, poultry, grains-beans, oils-sugars, fruits-nuts, fungi, leafy vegetables, root vegetables, sprouts, and vegetables from a vine or stalk.

“Determining the proportion of outbreak-associated cases of foodborne illness due to the various food commodities is an important step,” according to Patricia M. Griffin, MD, chief of CDC’s Enteric Diseases Epidemiology Branch.  “Identification of particular food commodities that have caused outbreaks can help public health officials and the food industry to target control efforts from the farm to the table.”

However, Griffin cautions that while this report is useful, only a small proportion of foodborne illnesses occur as part of recognized outbreaks. Moreover, some outbreaks are not detected, investigated, or reported because many states lack the resources to perform the work.

The full report, “Surveillance for Foodborne Disease Outbreaks - United States, 2006” appears in this week′s Morbidity and Mortality Weekly Report (June 12, 2009) and is available online at www.cdc.gov/mmwr.