The 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. Foodborne illness is a substantial health burden in the Untied States. In 2017, there were 24,484 infections, 5,677 hospitalizations, and 122 deaths attributed to food borne illness.
Commander with the time period of 2014 to 2016, FoodNet, the Foodborne Diseases Active Surveillance Network, showed that there was increase of infections with Campylobacter, Listeria, non-0157 Shiga toxin-producing Escherichia coli (STEC), Yersinia, Vibrio, and Cyclospora. This increased incidence may have resulted form the increased used and sensitivity of culture-independent diagnostic tests.
At the same time, the 2017 incidence of infections with Salmonella serotypes Typhimurium and Heidelberg decreased, and the incidence of infections with serotypes Javiana, Infantis, and Thompson increased. The report speculates that new regulatory requirements that include enhanced testing of poultry products for Salmonella may have contributed to the decreases.
The incidence of STEC 0157 infections during 2017 also decreased. That parallels reductions in isolates from ground beef. This, along with the decrease in the two Salmonella serotypes, “provide supportive evidence that targeted control measures are effective.” And the increases in some Salmonella serotypes give officials an opportunity to investigate infection sources and to design specific interventions.
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 and, oysters, and chicken liver. And Vibrio outbreaks sickened people through raw oysters and seafood.
Culture-Independent diagnostic test uses are increasing. In previous years, routine stool test only included methods for finding Salmonella, Campylobacter, Shigella, and STEC 0157. These panel tests more often include Cyclospora, Yersinia, Vibrio, and non-O157 STEC, which most likely drove the increased incidence in these infections in 2017.
But, CIDTs are unable to subtype pathogens, find antimicrobial susceptibility, and detect outbreaks when reflex culture isn’t performed. Isolates are needed to perform these types of tests. Because of this, the Association of Public Health Laboratories recommends that clinical labs culture CIDT-positive specimens. Results are more quickly obtained with CIDTs, which may account for increased incidence of these infections. Infections that may have been undetected with culture methods may be found with improved sensitivity and specificity of DNA-based CIDTs.
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. The declines in these infections and STEC o157 infections show that control measures work. More control measures are needed, and “might be achieved with continued implementation of the FDA Food Safety Modernization Act, new or revised meat and poultry performance standards, and enhanced training and guidance for industry and inspection personnel,” according to the report.
