Editor's note: the following is from a presentation by Katherine Marshall, MPH, and colleagues, U.S. Centers for Disease Control and Prevention, during the 2024 annual meeting of the American Association of Avian Pathologists.

Salmonella causes an estimated 1.03 million foodborne infections in the U.S. each year, and over 40% are attributed to the consumption of contaminated chicken, turkey, beef, and pork. Although more than 2,500 Salmonella serotypes have been described, the top 20 cause nearly 70% of U.S. Salmonella infections.

Most Salmonella infections are not linked to a recognized outbreak, but outbreak data provide definitive links to specific food sources. To determine which serotypes cause the most outbreak illnesses associated with specific food products and inform prevention measures, we developed an approach to categorize serotypes using outbreak illness burden (high, moderate, low) and trajectory (increased, stable, decreased).

Data were collected from Salmonella outbreaks reported to CDC's Foodborne Disease Outbreak Surveillance System during 2012-2021 with a single confirmed or suspected food vehicle of chicken, turkey, beef, or pork. For each meat and poultry type, the number of outbreak-associated illnesses were calculated for each serotype. Serotypes were considered highest priority for outbreak prevention if they were classified as high burden (≥75th percentile for number of outbreak illnesses among that product type during 2017-2021) and having an increased trajectory (illnesses increased ≥50% from 2012-2016 to 2017-2021).

During 2012-2021, we identified 192 foodborne outbreaks linked to chicken, turkey, pork, and beef resulting in 7,077 illnesses, 1,330 hospitalizations, and 9 deaths. Of these, 88 (46%) outbreaks and 2,935 (41%) illnesses were attributed to chicken and 24 (13%) outbreaks, and 1,188 (17%) illnesses were attributed to turkey.

For chicken, illnesses were caused by 19 serotypes. The serotypes Enteritidis, Infantis, and Blockley had high outbreak burden and increased trajectory so were considered highest priority for outbreak prevention; Typhimurium and Braenderup were classified as moderate outbreak burden and increased trajectory and were also considered high priority.

For turkey, illnesses were caused by 12 Salmonella serotypes, with two (Enteritidis, Reading), considered highest priority and one (Hadar) with moderate burden and increased trajectory, considered high priority for outbreak prevention. Two serotypes were identified to be recently emerged (caused outbreak illnesses during 2017-2021 but not during 1998-2011) for chicken (Blockley, Anatum) and two were identified for turkey (Anatum, Schwarzengrund).

By identifying and publishing outbreak illness burden and trajectory data annually, our goal is to facilitate prioritization of serotypes for prevention of outbreaks. Intensified prevention measures may be considered for serotypes with both high or moderate burden and increased trajectory.

These results are available to the public on CDC's BEAM dashboard: https://www.cdc.gov/ncezid/dfw...