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FoodNet Facts and Figures - Incidence trends

How are incidence trends examined in FoodNet?

FoodNet uses a main-effects, log-linear Poisson regression (negative binomial) model to estimate changes in the incidence of infection. The model adjusts for the increase in the number of FoodNet sites since 1996 and for variation in the incidence of infections among sites. The average annual incidence for 1) 19961998 (1997 1998 for Cryptosporidium), the first years of surveillance, and 2) a more recent 3-year period (20062008) are used for comparisons. Prior facts and figures on FoodNet surveillance data from 2008 and 2009 used the preceding 3 years, a moving period, for comparison; this report initiates use of 20062008 as a stable comparison period. The model is used to calculate the estimated change in incidence (relative rate) between 2010 and the comparison periods, with 95% confidence intervals (CI). In the figures that report percent change, the percent change for the current year is calculated by comparison with the appropriate comparison period and graphed along with the 95% confidence interval. In the figures that report relative rate, the relative rate for each year is graphed. Trends in STEC non-O157 and Cyclospora infection were not evaluated because of sparse data.

FoodNet also uses the negative binomial model to measure overall trends in incidence. In this model, data for Campylobacter, Listeria, Salmonella, STEC O157, Yersinia, and Vibrio, the bacterial pathogens for which >50% of illnesses are estimated to be transmitted by food, are combined, weighting them equallyweighting by incidence of infection for each pathogen.


Results:

By pathogen

Compared with 1996-1998 period

Figure 1. Percent change Adobe Acrobat Icon PDF 41KB

Figure 2. Relative rates (graph 1) Adobe Acrobat Icon PDF 29KB
Figure 3. Relative rates (graph 2) Adobe Acrobat Icon PDF 21KB

Compared with 2006-2008 period

Figure 4. Percent change Adobe Acrobat Icon PDF 28KB

Summary (both comparison periods)

Table 8. Percent change Adobe Acrobat Icon PDF 61KB
By Salmonella serotype

Compared with 1996-1998 period

Figure 5. Percent change Adobe Acrobat Icon PDF 27KB

Figure 6. Relative rates (graph 1) Adobe Acrobat Icon PDF 41KB
Figure 7. Relative rates (graph 2) Adobe Acrobat Icon PDF 37KB

Compared with 2006-2008 period

Figure 8. Percent change Adobe Acrobat Icon PDF 25KB

Summary (both comparison periods)

Table 9. Percent change Adobe Acrobat Icon PDF 64KB
Overall change in incidence
Overall change for 2010

Table 10. Percent change Adobe Acrobat Icon PDF 41KB
Figure 9. Relative rates Adobe Acrobat Icon PDF 37KB

 
 
Page last modified: January 30, 2012
Content source: Centers for Disease Control and Prevention
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)
Division of Foodborne, Waterborne, and Environmental Diseases (DFWED)
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1600 Clifton Road NE, MS C-09
Atlanta, GA 30333
Phone: +1(404) 639-2206
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Email: foodnet@cdc.gov

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