Researchers report Salmonella as top cause of foodborne illness deaths in 2019

New research shows there were 9.9 million domestically acquired foodborne illnesses in the United States in 2019. The most recent data available before this was published in 2011.

By estimating the number of foodborne illnesses, the Centers for Disease Control and Prevention can provide information on the critical allocation of resources, according to the researchers whose work was published in Emerging Infectious Diseases.

The researchers studied illnesses, hospitalizations and deaths caused by several major foodborne pathogens: Campylobacter spp., Clostridium perfringens, invasive Listeria monocytogenes, norovirus, nontyphoidal Salmonella serotypes, and Shiga toxin–producing E. coli (STEC).

Norovirus caused the most illnesses with 5.5 million cases followed by Campylobacter spp. with1.9 million illnesses, and nontyphoidal Salmonella serotypes with1.3 million illnesses. Researchers found that C. perfringens caused 889,000 illnesses, STEC 357,000, and invasive Listeria monocytogenes 1,250.

Norovirus was the leading cause of hospitalizations resulting from domestically acquired foodborne illnesses with 22,400 a year, followed by Campylobacter spp. with 13,000, nontyphoidal Salmonella with 12,500, STEC with 3,150, invasive Listeria monocytogenes with 1,070, T. gondii with 848, and C. perfringens with 338. Invasive Listeria monocytogenes caused 920 non–pregnancy-associated and 148 — 74 mothers and 74 infants — pregnancy-associated hospitalizations.

Domestically acquired, foodborne nontyphoidal Salmonella caused 238 deaths each year, followed by Campylobacter spp. with 197, norovirus with 174, invasive Listeria monocytogenes with 172, STEC with 66, T. gondii with 44, and C. perfringens with 41. The researchers estimated 166 nonpregnancy-associated deaths and 6 pregnancy-associated deaths, all among infants, caused by Listeria monocytogenes. In addition, they estimated 37 fetal deaths.

The true number of illnesses is underreported, according to the researchers, because not all sick people seek medical care or, if they do, they are not tested for foodborne pathogens. Also, illnesses might not be reported to public health surveillance systems. To overcome these challenges, the CDC periodically estimates the number of foodborne illnesses by adjusting for undercounts in surveillance data.

“Since the last estimates published in 2011, new data and methods have become available, and new regulations and other interventions to prevent foodborne illness have been implemented. Moreover, culture-independent diagnostic tests (CIDTs) have been more widely adopted, increasing the likelihood of identifying pathogens,” according to the research report.

The Interagency Food Safety Analytics Collaboration considers four pathogenic bacteria to be priorities for source attribution and actions by regulatory agencies: Campylobacter spp., Listeria monocytogenes, nontyphoidal Salmonella, and Shiga toxin–producing E. coli (STEC). For the assessment of 2019 foodborne illnesses the researchers also included norovirus, Clostridium perfringens, and Toxoplasma gondii because all seven pathogens were previously estimated to be the leading causes of domestically acquired foodborne illnesses, hospitalizations and deaths in the United States.

To determine the number of illnesses caused by Campylobacter spp., nontyphoidal Salmonella, and STEC, the researchers used 2017–2019 data from the Foodborne Diseases Active Surveillance Network, also known as FoodNet. FoodNet conducts active, population-based surveillance of laboratory-diagnosed infections at 10 sites equal to roughly 15 percent of the U.S. population.

The researchers used 2016–2019 data from the CDC’s nationwide Listeria Initiative surveillance system to determine the number of illnesses caused by invasive Listeria monocytogenes.

“Of 37.6 million estimated episodes of illness caused by Campylobacter spp., C. perfringens, invasive Listeria monocytogenes, norovirus, nontyphoidal Salmonella, and STEC infections, 9.9 million illnesses were estimated to be acquired domestically and were foodborne,” according to the research report.

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