2002 data show mixed results in battle against foodborne diseases

Apr 18, 2003 (CIDRAP News) – Preliminary data for 2002 indicate that the nation is making progress against some major foodborne diseases, including Campylobacter and Listeria, but not against others, including Salmonella, one of the most common.

On the basis of surveillance that includes about 13% of the US population, Campylobacter and Listeria infections have shown a sustained decline since 1996, the Centers for Disease Control and Prevention (CDC) reports in today's Morbidity and Mortality Weekly Report.

However, salmonellosis cases stayed about the same over the 7 years. In addition, the rates of Shigella, Vibrio, Cryptosporidium, and Escherichia coli O157 infections, as well as hemolytic uremic syndrome (HUS), a complication of E coli O157:H7 infections, have remained stable or increased, according to the report.

The case rates for campylobacteriosis and listeriosis are approaching the national health objectives for 2010, while rates for salmonellosis and E coli O157:H7 infections remain well above the objectives, CDC said.

Overall, the preliminary 2002 report presents a less rosy picture than the 2001 report the CDC published a year ago. At that time the agency reported that seven foodborne bacterial pathogens (Salmonella, Campylobacter, Shigella, E coli O157, Listeria, Yersinia, Vibrio) declined an overall 23% from 1996 through 2001, translating into tens of thousands fewer cases.

The figures are based on surveillance by FoodNet (the Foodborne Diseases Active Surveillance Network), which covers Minnesota, Oregon, Colorado, Maryland, New York, Tennessee, and selected counties in California, Connecticut, and Georgia. The network collects data on all laboratory-diagnosed infections with major foodborne pathogens, along with HUS. The combined population of the coverage area is 37.4 million.

A total of 16,580 cases of 10 infections were reported in 2002, the report says. These included 6,028 Salmonella cases, or 16.1 per 100,000 population, up from 15.1 per 100,000 last year. Case totals and rates for several other common pathogens and illnesses follow:

  • Campylobacter: 5,006 cases, 13.37 per 100,000 (13.8 in 2001)
  • Shigella: 3,875 cases, 10.34 per 100,000 (6.4 in 2001)
  • Shiga toxin–producing E coli O157: 647 cases, 1.73 per 100,000 (1.6 in 2001)
  • Cryptosporidium: 541 cases, or 1.42 per 100,000 (1.5 in 2001)
  • Listeria: 101 cases, or 0.27 per 100,000 (0.3 in 2001)
  • HUS: 44 cases, or 1.78 per 100,000 children under age 5 (0.9 in 2001)

The CDC used a regression model to estimate the overall change in incidence for each illness from 1996 through 2002. The model showed that Campylobacter cases decreased 24% over that time and Listeria cases decreased 38%. The incidence of Salmonella did not change significantly, while Shigella was 14% higher in 2002 than in 1996. E coli O157 incidence was 8% lower in 2002 than in 1996, but HUS rates did not change significantly.

Although the overall incidence of salmonellosis stayed about the same, the pattern of Salmonella strains shifted during the 7-year period, the report states. The incidence of S enteritidis serovar Typhimurium declined 31%, while S Newport increased 87%. S enteritidis declined until 1999 but then reversed direction to end at about the same levels in 2001 and 2002.

Several large illness outbreaks influenced the 2002 figures, the report notes. These included community outbreaks of Shigella sonnei infections in Georgia and Maryland; an outbreak of E coli O157 infections associated with a county fair in Oregon; an outbreak of multidrug-resistant S Newport infections from ground beef, possibly related to the emergence of this strain in dairy cattle; and a multistate outbreak of S Newport infections from contaminated tomatoes.

CDC says the findings are subject to several limitations. FoodNet surveillance captures only laboratory-diagnosed illnesses and therefore misses the majority of foodborne cases. In addition, some illnesses are acquired through things other than food, such as contaminated water, and the findings may not be representative of the entire US population.

CDC. Preliminary FoodNet data on the incidence of foodborne illnesses—selected sites, United States, 2002. MMWR 2003;52(15):340-3
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5215a4.htm

See also:

CIDRAP News (Apr 19, 2002): Foodborne bacterial disease rates dropped 23% from 1996 to 2001, CDC says

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