How are incidence trends examined in FoodNet?

FoodNet uses a main-effects, log-linear Poisson regression model (negative binomial) to estimate the incidence of the pathogens and syndrome under surveillance. This model controls for the increase in the number of FoodNet sites and its surveillance population since 1996 and for variation in the incidence of infections among sites. The average annual incidence for the previous 3 years (2004-2006) and for 1996-1998 (1997-1998 for Cryptosporidium), the first years of surveillance, are used as comparison periods. The fitted model is used to calculate the estimated change in incidence (relative rate) between 2007 and the comparison periods, along with 95% confidence intervals (CI).  For HUS surveillance, 2000-2001, the first years of surveillance, are used as the comparison period.  The information from the model is presented as figures.  In the percent change figures, the percent change for the current year is compared with the appropriate comparison period and graphed along with the 95% confidence interval.  In the relative rate figures, the relative rate for each year is graphed.

Results:

By pathogen

Compared with 1996-1998 period

Percent change PDF 24KB
Relative rates (2 graphs) PDF 21KB

Compared with 2004-2006 period

Percent change PDF 24KB

By Salmonella serotype

Compared with 1996-1998 period

Percent change PDF 24KB
Relative rates PDF 23KB

Compared with 2004-2006 period

Percent change PDF 25KB

By age group (Compared with 1996-1998 period) for selected pathogens

Campylobacter

Relative rates PDF 21KB

Salmonella

Relative rates PDF 21KB

Shiga toxin-producing Escherichia coli O157

Relative rates PDF 21KB

Shigella

Relative rates PDF 23KB

Post-diarrheal hemolytic uremic syndrome (HUS)

Post-diarrheal hemolytic uremic syndrome (HUS) surveillance, which began in 2000, is conducted in nine states through a network of pediatric nephrologists and infection-control practitioners, and is validated with a review of hospital discharge data. Because of the delay required for review of hospital records, this web page contains preliminary HUS data for 2006.

For HUS surveillance, 2000-2001, the first years of surveillance, are used as the comparison period when examining incidence trends. In 2006, the incidence of HUS Was not significantly different from the average incidence of 2000 and 2001.

Post-diarrheal hemolytic uremic syndrome (HUS) in children aged <5 years PDF 236KB