Annual data from the CDC's Foodborne Diseases Active Surveillance Network (FoodNet) show that Campylobacter and Salmonella caused the most reported bacterial foodborne illnesses in 2016.

FoodNet, which collects data on 15% of the US population, reported 24,029 foodborne infections, 5,512 hospitalizations, and 98 deaths in 2016. The numbers of reported illnesses by germ are: Campylobacter (8,547), Salmonella (8,172), Shigella (2,913), Shiga toxin-producing E. coli (1,845), Cryptosporidium (1,816), Yersinia (302), Vibrio (252), Listeria (127) and Cyclospora (55). This is the first time the report also includes in the total number of infections those foodborne bacterial infections diagnosed only by rapid diagnostic tests in FoodNet sites. Previously, the report counted foodborne bacterial infections confirmed only by traditional culture-based methods in the total numbers.

The new data reflect the increasing popularity of rapid tests known as culture-independent diagnostic tests, or CIDTs. These faster tests can have immediate benefits for treatment, but do not collect information needed to determine if an infection is antibiotic-resistant or if it is linked to an outbreak. Positive results on rapid tests can be followed up by culture-based tests to get detailed data, but often are not, according to the report.

“We need foodborne-illness trend data to monitor progress toward making our food supply safer,” Robert Tauxe, MD, MPH director of CDC’s Division of Foodborne, Waterborne, and Environmental Diseases said in a press release about the report. “It’s important that laboratories continue to do follow-up cultures on CIDT-positive patients so public health officials can get the information needed to protect people from foodborne illness.”

Foodborne illness remains a substantial public health concern in the United States. Previous analyses have indicated that the number of infections far exceeds those diagnosed; CIDTs might be making those infections more visible. However, the shift to CIDTs poses challenges to monitoring foodborne illness trends because changes in the number of new infections could reflect changes in testing practices rather than a true increase in infections. For this reason, comparisons of the 2016 data with data from previous years may not accurately reflect trends. Estimated infections this year and in years past are accurate, but cannot be directly compared because the total now includes results from diagnostic tests. FoodNet is developing new tools that will allow it to continue to track the needed progress toward reducing foodborne illness.

 

Reference

Marder EP, Cieslak PR, Cronquist AB, et al. Incidence and trends of infections with pathogens transmitted commonly through food and the effect of increasing use of culture-independent diagnostic tests on surveillance — Foodborne Diseases Active Surveillance Network, 10 US sites, 2013–2016. MMWR Morb Mortal Wkly Rep. 2017;66:397–403.