CDC just today published its 2006 data on Foodborne Disease Outbreaks. Here is the Report – no wonder I have been so busy:
Foodborne illnesses are a major health burden in the United States. Most of these illnesses are preventable, and analysis of outbreaks helps identify control measures. Although most cases are sporadic, investigation of the portion that occur as part of recognized outbreaks can provide insights into the pathogens, food vehicles, and food-handling practices associated with foodborne infections. CDC collects data on foodborne disease outbreaks (FBDOs) from all states and territories through the Foodborne Disease Outbreak Surveillance System (FBDSS). This report summarizes epidemiologic data on FBDOs reported during 2006 (the most recent year for which data have been analyzed). A total of 1,270 FBDOs were reported, resulting in 27,634 cases and 11 deaths. Among the 624 FBDOs with a confirmed etiology, norovirus was the most common cause, accounting for 54% of outbreaks and 11,879 cases, followed by Salmonella (18% of outbreaks and 3,252 cases). Among the 11 reported deaths, 10 were attributed to bacterial etiologies (six Escherichia coli O157:H7, two Listeria monocytogenes, one Salmonella serotype Enteritidis, and one Clostridium botulinum), and one was attributed to a chemical (mushroom toxin). Among outbreaks caused by a single food vehicle, the most common food commodities to which outbreak-related cases were attributed were poultry (21%), leafy vegetables (17%), and fruits/nuts (16%). Public health professionals can use this information to 1) target control strategies for specific pathogens in particular foods along the farm-to-table continuum and 2) support good food-handling practices among restaurant workers and the public.
State, local, and territorial health departments voluntarily submit reports of FBDOs using a web-based standard form to the electronic Foodborne Outbreak Reporting System (eFORS). An FBDO is defined as the occurrence of two or more cases of a similar illness resulting from the ingestion of a common food. Information regarding clinical syndromes, incubation period, and laboratory testing for various etiologic agents is available to guide reporting officials.* Officials report an etiology as either confirmed (at least one etiologic agent found) or suspected (based on clinical and epidemiologic information). Analysis was limited to FBDOs with a single etiology (i.e., suspected or confirmed). Food vehicles are food items linked to illnesses by an outbreak investigation. CDC classifies the foods vehicles implicated in outbreak reports into the following 17 food commodities: 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.
During 2006, public health officials reported a total of 1,270 FBDOs from 48 states. A confirmed or suspected single etiologic agent was indentified in 884 (70%) FBDOs (621 confirmed and 263 suspected), accounting for 22,510 (81%) cases. The number of outbreaks reported by each state or territory ranged from zero to 76. The median rate was 0.21 (range: zero to 1.3) per 100,000 population. For seven states (Hawaii, Maine, Minnesota, North Dakota, Oregon, Vermont, and Wisconsin), the rate of reporting was greater than three times the median. Rates of reported outbreaks varied markedly by etiology group. Among the 621 outbreaks (with 18,111 cases) with a confirmed single etiologic agent, 343 (55%) outbreaks and 11,981 (66%) cases were caused by viruses, 217 (35%) outbreaks and 5,781 (32%) cases were caused by bacteria, 52 (8%) outbreaks and 219 (1%) cases were caused by chemical agents, and nine (1%) outbreaks and 29 (1%) cases were caused by parasites. Calicivirus caused 337 (98%) of the confirmed FBDOs attributed to viruses; all calicivirus outbreaks reported in 2006 were attributed to norovirus. Salmonella, the most commonly reported bacterial etiologic agent, caused 112 (52%) of the confirmed FBDOs attributed to bacteria; Salmonella serotype Enteritidis caused the most outbreaks (28 [13%]). Shiga toxin–producing E. coli (STEC) caused 29 (13%) of confirmed FBDOs attributed to bacteria, of which 27 were serogroup O157.
Eleven multistate outbreaks, defined as outbreaks in which exposures occurred in more than one state, were detected; 10 of these were attributed to bacteria. One attributed to chemical agents was transmitted by baked goods contaminated by a floor sealant (11 cases). Four of the bacterial outbreaks were attributed to E. coli O157, of which three were transmitted by leafy vegetables (395 cases) and one was transmitted by beef (44 cases). Four were attributed to Salmonella, of which two were transmitted by tomatoes (307 cases), one by peanut butter (715 cases), and one by fruit salad (41 cases). An outbreak of Vibrio parahaemolyticus infections was transmitted by oysters (177 cases). An outbreak attributed to C. botulinum toxin was transmitted by carrot juice (four cases).
Public health officials identified a food vehicle in 528 (42%) FBDOs, of which 243 (46%) outbreaks with 6,395 (50%) cases were classified as having ingredients belonging to only one of the 17 commodities. Among the 243 outbreaks attributed to a single commodity, the most outbreaks were attributed to fish (47 outbreaks), poultry (35 outbreaks), and beef (25 outbreaks), and the most cases were attributed to poultry (1,355 cases), leafy vegetables (1,081 cases), and fruits/nuts (1,021 cases). Pathogen-commodity pairs responsible for the most outbreak-related cases were Clostridium perfringens in poultry (902 cases), Salmonella in fruits/nuts (776 cases), norovirus in leafy vegetables (657 cases), STEC in leafy vegetables (398 cases), Salmonella in vine-stalk vegetables (331 cases), and V. parahaemolyticus in mollusks (223 cases).
Although the dairy commodity accounted for only 3% of single commodity outbreak-related cases (16 outbreaks and 193 cases), 71% of dairy outbreak cases were attributed to unpasteurized (raw) milk (10 outbreaks and 137 cases). A wide range of bacterial pathogens were associated with unpasteurized milk outbreaks, including Campylobacter (six outbreaks), STEC O157 (two outbreaks), Salmonella (one outbreak), and Listeria (one outbreak), resulting in 11 hospitalizations and one death.
The largest outbreaks with a known etiology and single food commodity were attributed to baked chicken contaminated with C. perfringens (741 cases), peanut butter contaminated with Salmonella (714 cases), and spinach contaminated with E. coli O157 (238 cases). In the spinach outbreak, 31 persons developed hemolytic uremic syndrome, and five died, including a child. The contaminated spinach was traced back to a single farm, where the outbreak strain was isolated from nearby cattle feces and feral swine feces.