Stalled progress: Enteric infection reduction efforts slowed in 2022 despite pandemic easing

In a recent study published in the United States Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report, scientists compare the incidence of infections due to foodborne pathogens during 2022 to the average annual incidence between 2016 and 2018 in the U.S.

Study: Preliminary Incidence and Trends of Infections Caused by Pathogens Transmitted Commonly Through Food — Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 2022. Image Credit: Giovanni Cancemi / Shutterstock.com

How the COVID-19 pandemic impacted foodborne illnesses

Infections due to foodborne pathogens cause about 10 million infections each year in the U.S. and are responsible for over 50,000 hospitalizations and over 1,000 deaths. To control and prevent enteric infections, the U.S. Foodborne Diseases Active Surveillance Network (FoodNet) regularly monitors eight of the major foodborne pathogens in 10 sites across the U.S.

FoodNet reports that between 2020 and 2021, there was a significant reduction in the number of enteric infections. This reduction was largely attributed to the public health interventions, behavioral changes, and healthcare and testing practices implemented during the coronavirus disease 2019 (COVID-19) pandemic.

Following widespread COVID-19 vaccination, many of the travel restrictions and disease mitigation measures have been lifted. This has led to the resumption of international and local travel, as well as a relaxation of vigilance measures, thereby increasing the incidence of enteric infections.

About the study

The U.S. CDC, along with the health departments of 10 states, the U.S. Food and Drug Administration (FDA), and the Department of Agriculture’s Food Safety and Inspection Service (FSIS), conducted surveillance in the catchment area defined by FoodNet. This included over 50 million people tested in 2022, which constitutes about 15% of the U.S. population.

Bacterial cultures and culture-independent diagnostic tests (CIDT) were used to diagnose bacterial infections, while polymerase chain reaction (PCR) assays and microscopy were used to identify Cyclospora infections.

Data from the U.S. Census Bureau for 2021 and the total number of foodborne pathogen infections in 2022 were used to calculate infection incidence rates. Furthermore, a Bayesian approach was used to compare incidence rate changes between 2022 and 2016-2018 based on population changes and other trends.

The frequencies of foodborne pathogen-associated hospitalizations and deaths, as well as infections related to outbreaks and international travel, were calculated for each pathogen and overall. Hospital discharge information on post-diarrheal hemolytic uremic syndrome among adolescents and children was also used for the analysis, as the hemolytic uremic syndrome is a complication of Shiga toxin-producing Escherichia coli.

Rising foodborne pathogen infections in 2022

The annual incidence of infections caused by Salmonella, Listeria, Shigella, and Campylobacter were similar for 2022 and the years spanning 2016 to 2018. However, infections caused by Shiga toxin-producing Escherichia coli, Vibrio, Yersinia, and Cyclospora were higher during 2022 as compared to those reported between 2016 and 2018.

The highest infection incidence was for Campylobacter, with Salmonella infections second highest. While the overall incidence of infections was similar for Salmonella, Listeria, Campylobacter, and Shigella, Campylobacter infection incidence was the highest among domestically acquired infections. Infections from foodborne pathogens such as Vibrio, Yersinia, and Cyclospora also had higher incidences among infections that were domestically acquired.

Infection rates associated with deaths, hospitalizations, infections due to outbreaks, and those due to international travel were similar for 2022 and 2016-2018. However, the number of Salmonella infections that resulted in death was higher for 2022 than for 2016-2018 at 62 and 37, respectively.

Of the over 7,000 Salmonella infections reported in 2022, the five most common serotypes were the same as those reported in Salmonella infections since 2010.

Conclusions

The incidence rates of foodborne pathogenic infections associated with Salmonella, Listeria, Shigella, and Campylobacter in 2022 were the same as those reported between 2016 and 2018. However, the incidence of infections caused by Shiga toxin-producing Escherichia coli, Vibrio, Yersinia, and Cyclospora increased during 2022 after COVID-19 mitigation measures and travel restrictions had been lifted.

The study findings indicate that the progress in reducing the incidence of enteric infections has been slow. Furthermore, the incidence of Salmonella and Campylobacter infections in 2022 is higher than the 2030 Healthy People target for U.S.

Both Salmonella and Campylobacter infections are believed to be linked to poultry meat in the U.S. Thus, more stringent hygiene measures are needed to reduce the risk of foodborne bacterial contamination during poultry meat processing.

Current recommendations by the FSIS to reduce the likelihood of poultry meat contamination include the use of probiotics and prebiotics, vaccination initiatives in live birds to prevent the colonization of poultry by pathogenic bacteria, and efforts to minimize the contamination of bedding, poultry feed, and water. Other recommendations by the FDA include efforts to reduce the contamination of leafy greens by Salmonella.