An analysis of U.S. Centers for Disease Control and Prevention (CDC) data conducted by Trace One revealed which states have the highest reported rates of foodborne illness, which pathogens cause the greatest number of foodborne illnesses, and the months of the year in which foodborne illnesses are most common.

The analysis draws from CDC’s National Notifiable Diseases Surveillance System (NNDSS), a database of laboratory-confirmed reports of certain foodborne illnesses and other diseases submitted by state and local health departments. Specifically, Trace One researchers looked at national-level statistics taken from CDC’s preliminary weekly estimates for 2024, as well as finalized state-level statistics for 2019–2022.

Surveillance data for eight nationally notifiable foodborne pathogens were the focus of the analysis: Campylobacter, Salmonella, Shigella, Shiga toxin-producing Escherichia coli (STEC), Cryptosporidium, Cyclospora, Vibrio, and Listeria monocytogenes. Despite being a leading cause of foodborne illness, norovirus was excluded from Trace One’s analysis because it is not a nationally notifiable disease, and because cases are often mild and undiagnosed.

Access Trace One’s full analysis here.

Campylobacteriosis, Salmonellosis are Most Commonly Reported Foodborne Illnesses in the U.S.

Of the foodborne pathogens included in the analysis, Campylobacter and Salmonella were the most common causes of foodborne illness, with 2024 incidence rates of 23.4 cases and 17.9 cases per 100,000 people, respectively. Incidence rates for both Campylobacter and Salmonella increased in 2024, up from 22.1 and 16 in 2023, respectively.

In 2024, Shigella was reported at 6 cases per 100,000, followed by STEC (4.7), Cryptosporidium (3.5), Cyclospora (1.1), Vibrio (1), and L. monocytogenes (0.2). Though L. monocytogenes and Vibrio infections are rare, they are often severe.

U.S. Foodborne Illnesses are Most Common in Summer Months

Per Trace One, foodborne illnesses in the U.S. peak in the summer, with nearly one-third (33.1 percent) of all cases occurring between June and August in 2024. This seasonal trend may be driven by warmer temperatures that promote bacterial growth, increased outdoor food preparation, and a greater consumption of fresh produce, which does not undergo a final kill-step (i.e., cooking).

August had the highest number of reported cases at 12.4 percent, followed by June (11.3 percent) and July (9.4 percent). In contrast, winter months such as January and February saw the lowest case counts, accounting for 5 percent and 5.6 percent of the annual total, respectively.

The parasite Cyclospora, a risk factor for fresh produce, had an especially concentrated seasonal pattern in 2024, with nearly half of all infections reported in July alone.

South Dakota has the Highest Incidence of Foodborne Illness in the U.S.

Incidence rates of foodborne illness are especially high in the U.S. Northern Plains and Upper Midwest, per Trace One. According to aggregated data from the most recent four years of finalized NNDSS records, South Dakota reported the highest overall rate of foodborne illness at 92.2 cases per 100,000 people, more than double the national average of 48.8. Nebraska (74.4), Minnesota (66.6), and Wyoming (66.4) closely followed.

Other high-ranking states in terms of foodborne illness incidence include Vermont (62), Florida (61.9), Wisconsin (60.5), Montana (59.7), and New Mexico (58.8). States with large populations like New York (58.3) and California (48.9) fell near the national average, but still ranked among the top half of states (11^th and 21^st, respectively).

Low rates were observed in Michigan (33.3), Indiana (33.7), and Maine (33.6). Alaska reported the lowest rate in the nation at 27 cases per 100,000 people.

State-level incidence rates may be influenced by variations in food supply chains and dietary habits, as well as differences in public health infrastructure, disease surveillance practices, and how likely individuals are to seek healthcare. Therefore, geographic differences in incidence rates may not only reflect actual differences in disease burden, but also other variations.

In Another Analysis, Georgia Ranks First for Most Pathogen Contamination in Retail Meats

This most recent analysis closely follows the release of a separate state-level, foodborne pathogen-related analysis by Trace One.

Earlier in 2025, Trace One analyzed U.S. Food and Drug Administration (FDA) National Antimicrobial Resistance Monitoring System (NARMS) data to identify the U.S. states with the highest levels of pathogen contamination (specifically, Campylobacter, Enterococcus, Escherichia coli, and Salmonella) in retail meat. Georgia, South Carolina, and Tennessee topped the list.

The report also underlined trends in prevalence and antimicrobial resistance (AMR) for the four pathogens. A summary of the retail meat contamination analysis can be read here.