The U.S. Centers for Disease Control and Prevention (CDC) is examining trends of foodborne illness outbreaks for 2017 and describes changes in incidence since 2006 in its Morbidity and Mortality Weekly Report (MMWR) for March 23, 2018, focused on the latest data from the Foodborne Disease Active Surveillance Network (FoodNet). The report summarizes preliminary 2017 data on nine pathogens spread commonly through food, including changes in incidence since 2006.

The report and accompanying materials are now available at https://www.cdc.gov/foodnet/index.html.

Key Findings

  • In 2017, FoodNet received reports of 24,484 illnesses, 5,677 hospitalizations, and 122 deaths in its surveillance area, which includes 15% of the U.S. population.
  • The incidence of infection per 100,000 population was highest for Campylobacter (19.2) and Salmonella (16.0), followed by Shigella (4.3), STEC (4.2), Cryptosporidium (3.y), Yersinia (1.0), Vibrio (0.7), Listeria (0.3) and Cyclospora (0.3).  In 2017, incidence of Cyclospora was significantly higher, with a 489% increase. Yersinia increased by 166%, Vibrio by 54%, STEC by 28%, Listeria by 26%, and Campylobacter by 10%. There were several Campylobacter outbreaks in 2017, for example: some linked to pet store puppies, others to raw milk, oysters and chicken livers.
  • The number of infections diagnosed by CIDT, a newer type of test, is increasing. The overall number of Campylobacter, Listeria, Salmonella, Shigella, Vibrio, and Yersinia infections diagnosed by CIDT increased 96% in 2017 compared with the 2014–2016 average.
  • CIDTs are revealing many infections – such as those caused by Cyclospora, Yersinia, Vibrio, and STEC non-O157 – that would not have been diagnosed before because of limited testing.
  • The incidence of Salmonella infections overall did not change significantly, but there were significant changes among serotypes:
    • The incidence of infections caused by serotypes Typhimurium and Heidelberg has been decreasing since 2006–2008, with overall declines of more than 40% for both.  The number of infections with Salmonella Typhimurium and Heidelberg has been decreasing in FoodNet sites for at least 10 years, long before CIDTs were used to diagnose foodborne infections. Laboratories perform reflex culture on most CIDT-positive Salmonella infections, so it is unlikely that this decrease is related to changes in diagnostic testing. People get Salmonella Typhimurium and Heidelberg infections from a wide variety of food sources. The decline in infections caused by particular serotypes of Salmonella may be due to a combination of efforts by regulatory agencies and industry to make food safer.
    • Infections cause by serotypes Javiana, Thompson, and Infantis have all increased by more than 50% since 2006–2008.

The report ends by stating that most foodborne illnesses can be prevented. New regulations that are aimed at reducing contamination on poultry may have contributed to the decrease in infections by Salmonella Typhimurium and Heidelberg.

 

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