In 2022, US rates of some foodborne illnesses surpassed or returned to prepandemic levels, finds a Centers for Disease Control and Prevention (CDC)-led study published today in Morbidity and Mortality Weekly Report.
Through the Foodborne Diseases Active Surveillance Network (FoodNet), the CDC, 10 state health departments, the US Department of Agriculture's Food Safety and Inspection Service, and the Food and Drug Administration conducted population-based surveillance of roughly 51 million people in 2022. FoodNet monitors the incidence of lab-confirmed infections caused by eight foodborne pathogens at 10 US sites.
The team calculated the rate of foodborne illness by dividing the number of 2022 infections by 2021 Census Bureau population estimates for the surveillance area. They then compared the rates with average annual incidences from 2016 to 2018, the reference period for the US Department of Health and Human Services' Healthy People 2030 targets.
"During 2020–2021, FoodNet detected decreases in many infections that were due to behavioral modifications, public health interventions, and changes in health care–seeking and testing practices during the COVID-19 pandemic," the researchers wrote. "Many pandemic interventions ended by 2022, resulting in a resumption of outbreaks, international travel, and other factors leading to enteric infections."
Campylobacter incidence highest
The incidence of foodborne infections per 100,000 caused by Campylobacter, Listeria, Salmonella, and Shigella stayed the same in 2022 as from 2016 to 2018, but the incidence of illnesses caused by Cyclospora, Shiga toxin–producing Escherichia coli, Vibrio, and Yersinia rose.
FoodNet identified 25,479 infections, 5,981 hospitalizations, and 170 deaths in 2022. The incidence was highest for Campylobacter (19.2 cases per 100,000 people), followed by Salmonella. But when the researchers limited their data set to domestically acquired infections, Campylobacter incidence was higher during 2022 (incidence rate ratio [IRR], 1.07, as were rates of Yersinia, Vibrio, and Cyclospora.
Many pandemic interventions ended by 2022, resulting in a resumption of outbreaks, international travel, and other factors leading to enteric infections.
Relative to 2016 to 2018 rates, similar percentages of 2022 infections led to hospitalization (23.5% in 2022 vs 23.8%) and death (0.7% vs 0.5%) or were linked to outbreaks (4.3% vs 3.9%) or to international travel (12.4% vs 12.8%).
Salmonella deaths rose
Sixty-two Salmonella infections (0.7%) led to death in 2022, compared with an annual average of 37 (0.4%) from 2016 to 2018. Serotypes and characteristics of Salmonella infections resulting in death were comparable to those from 2016 to 2018.
Of 7,032 Salmonella cases in 2022, 6,345 isolates (90%) were subtyped, with the five most common serotypes being Enteritidis (2.7 cases per 100,000 people), Typhimurium (1.6), Newport (1.4), Javiana (0.9), and I 4,,12:i:- (0.6). These have been the five most common serotypes each year since 2010.
In 2021, 72 cases of post-diarrheal hemolytic uremic syndrome (HUS) among children younger than 18 years were reported (0.7 cases per 100,000; IRR relative to 2016–2018, 0.96), including 41 (57%) among those younger than 5 (1.5 per 100,000; IRR, 0.95). HUS, which is often caused by an E coli infection, damages the kidneys and can be fatal.
"The incidence of Salmonella infections during 2022 was above the Healthy People 2030 target," the researchers wrote. "Also during 2022, the incidence of the most common domestically acquired infections, those caused by Campylobacter (17.4 per 100,000 population), was above the Healthy People 2030 target of 10.9."
Poultry meat is most common cause of Campylobacter infections in many countries and the most common cause of Salmonella infection in the United States.
"Progress in reducing enteric infection incidence was not observed during 2022, as influences of the COVID-19 pandemic subsided," the study authors said. "Collaboration among food growers, processors, retail stores, restaurants, and regulators is needed to reduce pathogen contamination during poultry slaughter and to prevent contamination of leafy greens."
"Better understanding of reasons for decreased incidence of foodborne infections during the COVID-19 pandemic (2020–2021) that were not sustained during 2022 could help guide the creation of additional mitigation strategies," they concluded.