Apr 13, 2006 (CIDRAP News) – The incidence of most major foodborne diseases in 2005 changed little from the previous year and generally continued a slow decline from levels measured in the late 1990s, according to the Centers for Disease Control and Prevention (CDC).
As in past years, Salmonella infections were the most common foodborne illness, followed by Campylobacter cases. Shigella, Cryptosporidium, and Escherichia coli O157 infections ranked third, fourth, and fifth.
The data come from the CDC’s FoodNet surveillance system, which covers all or parts of 10 states with about 15% of the US population. The agency reported the data in the Apr 14 issue of Morbidity and Mortality Weekly Report, published today.
The CDC assesses trends in foodborne illness by comparing each year’s figures with data from 1996 through 1998, the first 3 years of the FoodNet active surveillance program. On that basis, the agency says the rates of Campylobacter, Salmonella, Listeria, and several other infections were lower in 2005 than in the baseline period, but most of the progress came before 2005.
The surveillance program identified a total of 16,614 laboratory-confirmed foodborne infections in 2005. Salmonella accounted for 6,471 cases, about 39% of the total. There were 5,655 Campylobacter cases, or about 34% of the total. The CDC reports 2,078 Shigella cases, 1,313 Cryptosporidium cases, and 473 cases of Shiga toxinñproducing E coli (STEC) O157. The remaining cases included Yersinia, STEC non-O157, Listeria, Vibrio, and Cyclospora.
The report shows 44 cases of hemolytic uremic syndrome, a major complication of E coli O157, among children in 2004, the latest data available. That compares with 52 cases reported in 2003.
A comparison of the 2005 data with the CDC data for 2004 shows little change in incidence for most of the pathogens. The rate of salmonellosis cases in 2005 was 14.55 per 100,000 people, compared with 14.7 in 2004. The 2005 and 2004 incidence rates for others are as follows: Campylobacter, 12.72 and 12.9; Shigella, 4.67 and 5.1; Cryptosporidium, 2.95 and 1.32 (13.2 per million); and E coli O157, 1.06 and 0.9.
The CDC said the big increase in incidence of Cryptosporidium cases in 2005 over 2004 was due to a large outbreak at a water park in New York last year.
Because the FoodNet surveillance area has increased greatly since 1996, the CDC uses a statistical model to estimate the changes in rates of foodborne infections since the baseline period. Using that method, the agency cites the following estimates of declines in foodborne infections: Yersinia, 49%; Shigella 43%; Listeria, 32%: Campylobacter, 30%; E coli O157, 29%; and Salmonella, 9%.
However, there are several caveats. One is that Vibrio cases have increased an estimated 41% since the baseline period. Further, most of the progress on the other illnesses occurred before 2005. For Campylobacter, most of the decline came before 2001, and the rate of Listeria cases in 2005 was higher than in 2002.
In addition, only one of the five most common Salmonella serotypesóTyphimuriumóhas declined significantly, the CDC said.