With COVID-19, what will 2020 bring?

According to FoodNet data published in the recent Morbidity and Mortality Weekly Report, in 2019, compared with the previous 3 years, the incidence of infections caused by pathogens transmitted commonly through food increased (for CampylobacterCyclospora, STEC, VibrioYersinia) or remained unchanged (for Listeria, Salmonella, Shigella).

These data indicate that Healthy People 2020 targets for reducing foodborne illness will not be met.

Serotype Enteritidis has been the most common cause of Salmonella infections at FoodNet sites since 2007 and incidence has not decreased. Eggs were the major source of Enteritidis infections in the 1980s. Chicken was recognized as another important source during the late 1990s. Infantis moved from the ninth most common Salmonella serotype among infected persons during 1996–1998 to the sixth most common in 2019. Many infections are now caused by a new, highly resistant strain found in chicken. The incidence of some serotypes has declined. Typhimurium moved from the most common serotype during 1996–1998 to the third most common in 2019. Heidelberg, the third most common serotype during 1996–1998, is no longer among the top 20. These decreases might be partly related to the widespread practice of vaccinating chickens against Typhimurium, which shares antigens with Heidelberg. This observation, combined with a marked decline in Enteritidis infections in the United Kingdom after implementation of widespread chicken vaccination and improved farm hygiene, suggests that targeting other serotypes through poultry vaccination could be one way to reduce human illnesses in the United States.

Laboratory-diagnosed non-O157 STEC infections continue to increase. Although STEC O157 infections appear to be decreasing, outbreaks linked to leafy greens continue.

Produce is also an important source for CyclosporaListeria, and Salmonella. Although adoption of syndromic panels could be contributing to the large increase in Cyclospora, increased exposure to this pathogen cannot be excluded. Continued implementation of FDA’s Produce Safety Rule (e.g., expanded surveillance inspections of foreign and domestically grown produce) is needed, as are innovative approaches for preventing contamination.

Advances in laboratory science continue to revolutionize enteric disease clinical diagnostics and surveillance. Many laboratories now use CIDTs to detect infections that would have previously been undiagnosed. In 2019, public health laboratories fully transitioned the standard subtyping method for clinical bacterial isolates from pulsed-field gel electrophoresis to WGS. WGS provides detailed information to more effectively recognize outbreaks, determine resistance patterns, and investigate reoccurring, emerging, and persisting strains. However, because CIDTs do not yield isolates needed to perform WGS, the full potential of these new technologies can only be realized when laboratories are fully able to culture CIDT-positive specimens.

With health officials now focused (understandably) on the COVID-19 pandemic, it will be interesting to see if foodborne illnesses decline in 2020 and the cause of the decline..