Key Findings
- From 2014–2022, contamination before food preparation, particularly from animals or the environment, was the biggest contributor to foodborne illness outbreaks in the US.
- Viral outbreaks, often caused by sick food workers, decreased sharply during the COVID-19 pandemic, likely due to enhanced hygiene protocols.
- Inadequate food temperature control remains a leading factor in bacterial outbreaks, especially during cooking and cooling.
Why Do Foodborne Illness Outbreaks Still Happen?
Washing Hands
Each year, the U.S. sees roughly 800 foodborne illness outbreaks, resulting in around 15,000 illnesses, 800 hospitalizations, and 20 deaths. While these outbreaks represent a small portion of total foodborne illnesses, they give us a critical window into how and why foods become unsafe.
Symptoms of food poisoning typically include nausea, vomiting, diarrhea, stomach cramps, and sometimes fever, often appearing within hours to days after eating contaminated food.
A new CDC analysis of data from the National Outbreak Reporting System (NORS) for between 2014 and 2022 breaks down these outbreaks to reveal patterns in contamination, food handling errors, and how the COVID-19 pandemic could have affected recent trends.
How the Study Was Conducted
The CDC examined 2,677 foodborne illness outbreaks where investigators identified the underlying causes referred to as contributing factors. These fell into three main categories:
- Contamination: Pathogens introduced into food, often through raw ingredients, environmental exposure, or infected food handlers.
- Proliferation: Conditions that allowed bacteria to grow, such as improper storage or food held too long at unsafe temperatures.
- Survival: Failures in cooking or processing that allowed harmful microbes to remain in the final product.
Outbreaks were examined across three time periods:
- 2014–2016
- 2017–2019
- 2020–2022 (pandemic period)
Top Contributor: Contamination Before Preparation
The most common cause of foodborne outbreaks was food already contaminated before reaching the kitchen, typically by animals or environmental sources (e.g., norovirus from a salad bar, salmonella in cantaloupe). This type of contamination rose steadily from 22% to over 32% between 2014 and 2022.
These results point to the need for better safety practices before harvest, tighter controls during food processing, and reliable cooking methods, especially when handling high-risk items like leafy greens, raw milk, and seafood.
Ill Food Workers and Viral Outbreaks
Norovirus, a common cause of foodborne illness, is often spread by infectious food workers, especially through bare-hand contact.
From 2014–2019, nearly half of all viral outbreaks were linked to sick food workers. But by 2020–2022, this dropped significantly. Why? Likely due to pandemic-related measures like:
- Increased glove use
- Enhanced handwashing
- More aggressive worker exclusion policies
- Temporary closures of dining rooms
Interestingly, the use of gloved hands, not just bare hands, emerged as the top viral contamination source in the pandemic period, a reminder that gloves don’t replace good hygiene.
Bacterial Outbreaks: Heat Still Matters
For bacterial illnesses, improper cooking and cooling remained the biggest culprits:
- Allowing food to sit at unsafe temperatures during prep or service
- Inadequate heating during cooking
- Poor cooling practices for leftovers
Although these factors have persisted over the years, the pandemic may have made them worse. Staffing shortages and longer food holding times in institutional settings (like nursing homes or schools) may have increased risks during COVID-19.
What Can Be Done to Prevent Outbreaks?
The CDC recommends a multi-pronged approach:
- Restaurants and food services should follow FDA Food Code guidelines and implement Hazard Analysis and Critical Control Point (HACCP) plans.
- Managers should adopt written sick-leave policies and address barriers like income loss that prevent workers from staying home when sick.
- Health departments can strengthen inspection routines and provide ongoing training to detect risks like improper cooling or cross-contamination.
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FAQs
What’s the number 1 cause of foodborne illness outbreaks in the U.S.?
Contamination from animals or the environment before food preparation, especially in raw produce and seafood.
Did COVID-19 reduce foodborne illnesses?
Yes, especially viral outbreaks. Increased hygiene, glove use, and restaurant closures helped reduce norovirus transmission.
What role do sick food workers play?
A major one. They were responsible for a large portion of viral outbreaks, especially before 2020.
What temperature should food be cooked to?
It varies, but poultry should reach 165°F (73.9°C). Always use a food thermometer to verify.
What are the symptoms of food poisoning?
Common symptoms include nausea, vomiting, diarrhea, stomach cramps, and sometimes fever. Onset can range from hours to days after exposure.
Are certain foods more risky than others?
Yes. Leafy greens, raw milk, undercooked meats, and shellfish are commonly linked to outbreaks due to higher contamination risks.
Why do food safety failures keep happening?
Many failures are systemic—understaffed kitchens, lack of enforcement, or economic pressures that prevent sick workers from staying home.
What can restaurants do to prevent outbreaks?
Follow the FDA Food Code, implement Hazard Analysis and Critical Control Points (HACCP) plans, train staff on safe practices, and enforce sick leave policies.
Can foodborne illnesses be prevented at home?
Yes. Practice safe food handling: wash hands, keep raw meat separate, cook to safe temperatures, and refrigerate leftovers promptly.
Is handwashing or glove use more effective?
Both are important, but handwashing is critical. Gloves can still spread pathogens if hands are contaminated before use.
Bottom Line
The problem isn’t knowledge—it’s accountability. We know how to prevent foodborne illness, but outdated systems, limited enforcement, and weak oversight let the same failures repeat. Protocols exist, but without real consequences, they’re easy to ignore.
But what could fix this problem? Thermal imaging cameras that detect unsafe cooling in real time. Wearable biosensors that flag when food handlers are sick or feverish. AI-powered kitchen monitors that track violations before inspectors arrive. These technologies exist, but they’re rarely deployed outside of elite or chain operations.
The real issue is structural. Sick workers clock in because missing a shift means missing rent. Cooling failures happen because there’s no backup staff to monitor food safety. Training won’t fix what’s broken. The real problem is structural: low-wage labor, aging equipment, and regulations that don’t bite.
This isn’t just a list of weak spots—it’s a reality check. The system expects compliance without giving people the tools or support to actually follow through. That gap is why outbreaks keep happening.
References
Holst, M. M., Wittry, B. C., Crisp, C., Torres, J., Irving, D. J., & Nicholas, D. (2025, March 13). Contributing factors of foodborne illness outbreaks – National Outbreak Reporting System, United States, 2014–2022. MMWR Surveillance Summaries, 74(1), 1–12. https://doi.org/10.15585/mmwr.ss7401a1
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