Apr 29, 2004 (CIDRAP News) The incidence of Escherichia coli O157:H7 infections dropped 36% from 2002 to 2003, and long-term declines in the rates of several other common foodborne illnesses continued in 2003, the CDC reported today.
"The decline in E coli infections is very promising, though it's too early to say if it'll be sustained," Robert Tauxe, chief of the CDC's Foodborne and Diarrheal Diseases Branch, said at a news briefing. "The decline we observed between the beginning of our surveillance [in 1996] and 2003 was statistically significant for the first time."
CDC officials said their data also show declines over the past 8 years in Campylobacter, Salmonella, and Yersinia infections, as well as E coli O157:H7 cases. Rates for Listeria and Shigella infections did not change significantly over that time, and Listeria increased from 2002 to 2003, the agency said.
Federal officials cited a number of regulatory steps in recent years as probable reasons for the measured improvements. The CDC report noted that the US Department of Agriculture (USDA) ordered ground beef plants to reassess their systems for preventing E coli contamination in late 2002. That order followed a massive ground beef recall by a ConAgra plant in Greeley, Colo., in July 2002 and signs that E coli contamination in meat was more common than previously believed.
The CDC data, published in the Apr 30 issue of Morbidity and Mortality Weekly Report, come from the Foodborne Diseases Active Surveillance Network, or FoodNet, which covers about 14% of the US population. The network includes all or parts of nine states (California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New York, Oregon, and Tennessee), with about 41 million people. The network collects data on all laboratory-diagnosed cases of common foodborne illnesses.
FoodNet identified 15,600 cases of infections caused by nine pathogens in 2003. The numbers of cases and the incidence rates for the most common illnesses were as follows:
- Salmonella, 6,017 cases; 14.5 cases per 100,000 people
- Campylobacter, 5,215 cases; 12.6 per 100,000
- Shigella, 3,021 cases; 7.3 per 100,000
- Cryptosporidium, 480 cases; 10.9 per 100,000
- E coli O157, 443 cases; 1.1 per 100,000
- Yersinia, 161 cases; 4.0 per million
- Listeria, 138 cases; 3.3 per million
- Vibrio, 110 cases; 3.0 per million
The CDC said the number of FoodNet sites and the population under surveillance have increased since the network was launched in 1996, preventing simple calculation of long-term trends in the illness rates. Therefore the agency used a statistical regression model to estimate the trends from 1996 through 2003. The estimation method revealed that:
- Yersinia infections decreased 49% (95% confidence interval [CI], 61% to 34% decrease)
- E coli O157 decreased 42% (95% CI, 58% to 19% decrease), with most of the decrease occurring in 2003
- Campylobacter dropped 28% (95% CI, 36% to 20% decrease)
- Salmonella declined 17% (95% CI, 26% to 7%)
The incidence of Listeria infections increased in 2003 after dropping for the previous 4 years, the CDC said. Rates for Shigella and Listeria did not change significantly over the 8 year period. But Vibrio infections increased 116% over that span (95% CI, 24% to 276% increase), the report said.
Children were disproportionately affected by some infections, as in previous years, the CDC said. The incidence of Salmonella infections per 100,000 was 122.7 for infants (under 1 year) and 50.6 for children aged 1 to 4 years, compared with 10.8 for everyone else. The rates of Yersinia and E coli cases were also much higher for babies and small children than for older people.
In a news release, the CDC cited the launching of the USDA's Hazard Analysis/Critical Control Point (HACCP) system for meat and poultry plants in 1997 as a likely factor in the improving illness rates.
Speaking at the briefing, Elsa Murano, USDA undersecretary for food safety, said the USDA saw a decline in E coli in ground beef samples from 0.78% in 2002 to 0.3% in 2003, she said. She noted that the sampling program does not necessarily represent the meat supply nationwide.
"I will stress that we believe strongly that a lot of these declines, especially in E coli, over the last year have been the direct result of our policies to control the specific pathogens," Murano said. She said the required reassessment of HACCP plans in 2002 led to changes in ground beef plants.
In addition, a new training program for USDA inspectors, called Food Safety Regulatory Essentials, has "tremendously improved" training, Murano said. She also credited industry efforts, including an "E coli summit" meeting in 2003.
Tauxe said more people are using meat thermometers when they cook and food handlers may also be washing their hands more often, "but those differences have not been huge." He suggested that decreases in contamination of meat and poultry in production and processing have probably been more important factors.
The CDC noted that while the FoodNet data are the most detailed available, they may not accurately represent nationwide illness patterns. In addition, the data represent only laboratory-diagnosed cases; most foodborne illness cases are not lab-diagnosed.
CDC. Preliminary FoodNet data on the incidence of infection with pathogens transmitted commnonly through foodselected sites, United States, 2003 [Full text]
CDC's preliminary FoodNet data on incidence of foodborne illness in 2002