Data collected by the CDC's Emerging Infections Program Foodborne Diseases Active Surveillance Network (FoodNet) suggest that the incidence of foodborne illnesses under surveillance declined during 1999 compared with 1996. The decline is attributed primarily to decreases in campylobacteriosis and shigellosis.
According to the CDC: "Decreases in the incidence of foodborne illnesses occurred concurrently with disease prevention efforts, including implementation of changes in meat and poultry processing plants, new requirements for food service establishments, and increased attention to good agricultural practices for produce and eggs on farms."
FoodNet collects data on nine foodborne diseases in selected US sites. The data indicate substantial regional variations in the incidence of foodborne illness.
The following highlights were taken from the CDC Morbidity and Mortality Weekly Report, Vol 49, No. 10.
During 1999, 10,697 laboratory-confirmed cases of nine diseases under surveillance were identified: 4,533 of salmonellosis, 3,794 of campylobacteriosis, 1,031 of shigellosis, 530 of Escherichia coli O157 infections, 474 of cryptosporidiosis, 163 of yersiniosis, 113 of listeriosis, 45 of Vibrio infections, and 14 of cyclosporiasis.
Among the 4,095 Salmonella isolates serotyped, 982 (24 percent) were serotype Typhimurium, 403 (10 percent) were serotype Enteritidis, 362 (9 percent) were serotype Newport, 284 (7 percent) were serotype Heidelberg, and 231 (6 percent) were serotype Muenchen; and 405 (10 percent) of Salmonella isolates were untyped.
Among the 949 Shigella isolates with a known species, 626 (66 percent) were S sonnei and 295 (31 percent) were S flexneri.
For all reporting sites in 1999, incidence per 100,000 population was highest for salmonellosis (17.7), campylobacteriosis (14.8), and shigellosis (4.0). Substantial variation in incidence was observed among the sites for some pathogens.
From 1996-1999, the incidence of three laboratory-confirmed infections under surveillance declined substantially in the five original FoodNet sites. The incidence of Campylobacter declined 26 percent, shigellosis decreased 44 percent, S sonnei decreased 52 percent, and S flexneri declined 25 percent. Rates of E coli O157 infection decreased 22 percent. The overall incidence of salmonellosis decreased 15 percent from 1996-1998; however, the incidence increased 20 percent from 1998-1999.
The incidence of listeriosis, Vibrio infections, and yersiniosis was unchanged during the four-year period. Comparing the data on parasitic diseases from 1997-1999 (using only the sites reporting in all three years), rates of Cyclospora infections decreased 70 percent, and rates of Cryptosporidium infection were constant.
From 1998-1999, although S Typhimurium rates were steady and S Enteritidis rates declined, salmonellosis rates increased in all original FoodNet sites except California. The reasons are unclear, but in 1999 several large salmonellosis outbreaks were traced to unpasteurized orange juice, mangos, and raw sprouts.
In 2000, selected counties in Tennessee and Contra Costa County, California will be added to the FoodNet area, bringing the surveillance population to approximately 29 million persons—11 percent of the US population (1998 estimates).
The FoodNet site on the Web is http://www.cdc.gov/foodnet/.