The old saying goes, “You are what you eat.” That saying couldn’t be any more accurate than when it relates to foodborne illnesses, but the reality is that nobody likes a case of food poisoning.
Keeping your customers healthy should be a top priority whether you’re a chef, server, or line cook. But with so many different types of bacteria and viruses floating around, that’s easier said than done.
There’s a specific group of pathogens that account for a disproportionate number of serious foodborne illness outbreaks in foodservice.
They’re known as the “Big Six,” and they’re singled out in the FDA Food Code for a reason.1 These aren’t edge cases, the ones that pop up every now and then. These are the illnesses that are the most likely to move quickly through your operation if your systems aren’t tight.
Aside from those "Big Six" top offenders, there are plenty of other bugs to watch out for. From nausea-inducing norovirus to salmonella’s sneaky stomach ache, we’ll break down the most common foodborne illnesses in this post so you can keep everybody happy, healthy–and well-fed.
What are the "Big Six" foodborne illnesses?
7 other foodborne illnesses to watch out for
Why knowing the Big Six foodborne illnesses matters
How to protect yourself and your customers from foodborne illnesses
What to do if there’s a foodborne illness outbreak
What is a foodborne illness?
A foodborne illness is any illness caused by consuming contaminated food or beverages. There are more than 250 foodborne diseases, some more common than others.
A foodborne illness can manifest with a variety of different symptoms and can be caused by all kinds of factors. It might be that the food wasn’t stored properly or cooked to the correct temperature. Maybe one of the ingredients was spoiled. Perhaps the food was contaminated before it even got to the kitchen.
Foodborne illnesses can lead to issues such as nausea, vomiting, fever, and diarrhea. In some cases, they can even be life-threatening, particularly for those with weakened immune systems (like older adults or those who are immunocompromised in some other way).
Long story short–foodborne illnesses are dangerous and must be treated as such. Around 128,000 people are hospitalized each year in the United States due to foodborne illnesses, and sadly, many of these cases originate in restaurants and other foodservice establishments (not in our own personal kitchens).1,2
Keep reading to learn more about preventing this from becoming an issue in your establishment.
What are the "Big Six" foodborne illnesses?
The “big six” refers to six pathogens identified by the FDA as particularly high risk in foodservice environments: Norovirus, Salmonella Typhi, nontyphoidal Salmonella, Shigella, Shiga toxin-producing E. coli (STEC), and Hepatitis A.
These pathogens are treated differently in the FDA Food Code because they share a few critical traits.1 They spread easily, often through infected food handlers and require very little exposure to cause illness. And they’re repeatedly linked to outbreaks in restaurants, cafeterias, and other foodservice settings.
In other words, these aren’t rare or theoretical risks but are the common ones, the ones most likely to show up when something in your system breaks down.
Because of that, the FDA imposes stricter requirements on employee health reporting, exclusion policies, and hygiene practices related to these illnesses, not to create more rules but to control the risks that have the greatest impact when left unchecked.
1. Norovirus
Norovirus is the one most operators eventually encounter, whether that’s directly or indirectly. It’s the leading cause of foodborne illness outbreaks in the U.S., and it spreads quickly in environments where people and food intersect constantly.4
The challenge with norovirus is how easily it moves. It can live on surfaces longer than you expect, it takes very little to infect someone, and it’s often transmitted through ready-to-eat foods handled after preparation. This means a single breakdown in hand hygiene can ripple outward fast.
2. Nontyphoidal Salmonella
Salmonella shows up in two forms on the big six list, and both matter for different reasons.
The version most people recognize (nontyphoidal Salmonella) is commonly linked to undercooked poultry, eggs, or cross-contamination between raw and ready-to-eat foods. It’s a reminder that temperature control and separation aren’t just technical requirements; they’re what stand between routine prep and a preventable incident.
3. Salmonella Typhi
Salmonella Typhi is less common, but more severe. It causes typhoid fever and is typically spread through infected individuals rather than just contaminated ingredients. This is where employee health policies become a cornerstone of food safety: if someone carries it, knowingly or not, and continues handling food, the consequences can escalate quickly.
4. Shigella
Shigella spreads easily through poor hygiene and has a very low infectious dose, meaning it doesn’t take much exposure to cause illness. Again, handwashing is key when it comes to preventing this disease in your establishment.
5. STEC (E. coli)
Shiga toxin-producing E. coli (STEC) is a foodborne illness often associated with undercooked ground beef or contaminated produce like leafy greens.
What makes it particularly concerning is how severe the illness can become, especially for vulnerable populations. Found in the intestines of both humans and animals, pathogenic E.coli causes around 265,000 reported illnesses each year and is the leading cause of bladder infections.6
6. Hepatitis A
Although sometimes considered only as a sexually transmitted disease, Hepatitis A also commonly spreads through food and water, namely through the fecal-oral route (in other words, when an infected person doesn’t wash their hands well after using the restroom).4
This disease behaves differently from the others in that it affects the liver and has a longer incubation period. Someone can be contagious before they even realize they’re sick. That delay creates a wider window for transmission, especially if proper hygiene and reporting protocols aren’t in place.
Why knowing the Big Six foodborne illnesses matters
In a busy kitchen, there are dozens of potential hazards at any given moment. But the big six stand apart because they behave differently than most other foodborne risks.
They don’t necessarily come from ingredients. In fact, more often, they’re introduced by people, and in a wide variety of potential ways: an employee comes to work feeling slightly off, assumes it’s nothing, and pushes through the shift. Someone skips a full handwash because the line is backing up. Or a surface gets wiped, but not properly sanitized.
None of these moments feel significant on their own. But with the big six, they don’t need to be.
What makes these pathogens especially risky is how little it takes for them to spread. A small amount of contamination can affect dozens, or hundreds, of people. And because several of them can be transmitted even when symptoms are mild or not yet visible, they’re harder to catch through instinct alone.
That’s why the Food Code places so much emphasis on employee health, hygiene, and controlled processes for these specific illnesses. They exploit gaps in systems, not just one-off mistakes.
7 other foodborne illnesses to watch out for
The good news is that most of these can be prevented in the same way you’d prevent norovirus–by washing your hands, sanitizing regularly, and preventing cross-contamination.
Nevertheless, it’s essential to be aware of these culprits so you can do everything in your power to keep them off the menu–and off your mind. Here’s what to watch out for.
1. Campylobacter
This bacterium causes food poisoning and can lead to severe diarrhea, abdominal pain, and fever. In some cases, it can even lead to more severe health complications like Guillain-Barré syndrome.7
So, what are the common causes of Campylobacter? This bacterium is found in raw or undercooked meat and poultry products, unpasteurized milk, and contaminated water. It's important to cook meat and poultry to the proper temperature and always to practice good hygiene when handling food products.
2. Listeria
You can find Listeria in soil, water, and even certain animals, such as cows and poultry. It can also be present on produce that has been contaminated, as well as on processed meats and dairy products. For example, you often hear about listeria outbreaks on products like deli meat.
So, what are the symptoms if someone becomes infected with Listeria? The most common symptoms are fever, muscle aches, and gastrointestinal issues such as nausea and diarrhea.
However, it can also lead to more severe complications such as meningitis and sepsis, particularly in vulnerable groups such as pregnant women, older adults, and those with weakened immune systems.
3. Clostridium perfringens
Clostridium perfringens is another common bacteria that can wreak havoc on our customers’ meals if not handled properly. It thrives in environments with low oxygen, making it a prime culprit for improperly stored or reheated foods. That means that keeping food at the right temperature is crucial in preventing the growth of this harmful pathogen.
Clostridium Perfringens can cause a range of uncomfortable symptoms such as abdominal pain, diarrhea, nausea, and vomiting. Symptoms typically appear anywhere from six to 24 hours after consuming contaminated food but can last several days.
4. Staphylococcus aureus
Staphylococcus aureus is a type of bacteria found in the nose and on the skin of humans. It can be transmitted to food through improper handling or poor hygiene practices. When food is contaminated with Staphylococcus aureus, it can cause food poisoning symptoms like vomiting, diarrhea, and stomach cramps.
5. Toxoplasma gondii
Toxoplasma gondii is a parasitic infection that can affect both humans and animals, including livestock and poultry. The leading cause of this infection is ingesting food or water contaminated with the parasite or through contact with infected animals.
The symptoms of Toxoplasma gondii can vary from mild flu-like symptoms to severe neurological implications, including seizures and mental disorders. Pregnant women and individuals with weakened immune systems are at a higher risk of developing severe health complications.
6. Yersinia
Yersinia, also known as Yersiniosis, is a bacterial infection that can affect animals and humans. It is caused by the Yersinia bacteria, which can be found in various foods like raw or undercooked meat, poultry, and fish.
The symptoms of Yersinia infection generally start within three to seven days after being exposed to the bacteria and include fever, abdominal pain, diarrhea, nausea, and vomiting. In some rare cases, the infection can lead to more serious complications like reactive arthritis.
7. Cyclospora
Last but not least, we have Cyclospora. That is a parasite typically found in contaminated water or food that has been exposed to contaminated water, such as produce that has been rinsed in it. The parasite is most commonly found in tropical and subtropical regions. Still, as our food system becomes increasingly connected on a global level, cases have been popping up all over the world in recent years.
As for symptoms of Cyclospora, they often include stomach cramps, diarrhea, nausea, and fatigue. In some cases, the symptoms can last for weeks or even months. It's important to note that not everyone infected will experience symptoms, but they can still spread the parasite to others.
How to protect yourself and your customers from foodborne illnesses
Now that you know some of the most common foodborne illnesses that can affect your customers, let’s take a more detailed look at how to prevent them.
Keep things clean
First things first, "Keep things clean." That might sound like common sense, but it's worth reiterating. Proper hygiene practices are vital to preventing the spread of harmful bacteria and viruses.
According to the National Library of Medicine, about 64% of foodborne illness outbreaks are associated with poor health and hygiene practices.8
Ensure all surfaces, utensils, and equipment are regularly cleaned and sanitized. Frequently washing your hands is crucial, especially after handling raw meat or using the toilet.
Separate “cleaning” from “sanitizing” in your procedures. Define contact times for sanitizers and verify them with test strips where applicable.
Separate ingredients
Keep meats, poultry, seafood, and eggs separate from fruits and vegetables to prevent cross-contamination.
Store raw meats at the bottom of the fridge so any drips won't contaminate other foods, and always use separate cutting boards and utensils for different ingredients.
Cook food to the proper temperatures
Undercooked meat, poultry, and seafood can contain harmful bacteria that cause food poisoning.
Use a thermometer to check that food is cooked to the appropriate internal temperature, and keep hot food hot (above 60°C) and cold food cold (below 5°C).
Ensure good staff hygiene
Proper uniform and hair coverings are also important, as are proper hand-washing protocols. Set specific triggers (after handling raw food, after touching face or phone, after clearing tables) and reinforce them during service. Managers should actively observe and correct in real time.
Mandate glove and utensil use
Eliminate ambiguity. If it’s ready-to-eat, it requires gloves, deli tissue, or utensils, every time. There should be no exceptions based on experience level.
Require symptom reporting
About 40% of US foodborne illness outbreaks are traced back to workers who came in sick.10
Long story short here? It’s not worth it. Encourage your staff to stay home if they're sick and provide them with sick days. Use a simple check-in question or log. Make it clear that reporting illness will not be penalized.
Chill food that needs it
Chilling food is just as important as cooking it. Keep perishable items like meat, dairy, and produce stored at the correct temperature, and ensure they don't reach the 'danger zone' (between 4°C and 60°C).
Proper temperature regulation applies during transport, so ensure you or your suppliers transport food in a chilled environment when needed.
Streamline and standardize everything
Make the standards easier to follow than they are to ignore. Place hand sinks within immediate reach of workstations, gloves stocked and visible at every station, and post simple, task-specific reminders exactly where the work is happening (and not just in a handbook). Assign responsibility for the checks (e.g., one person verifies sanitizer levels each shift).
When you build your systems this way, compliance becomes the default behavior and there’s no opportunity for team members to “forget” what they need to do.
Treating food safety performance as part of daily operations with short, repeatable touchpoints (ie, a 2-minute reminder during pre-shift about handwashing triggers or quick corrections in the moment, as slip-ups happen) can go a long way.
What to do if there’s a foodborne illness outbreak
Even with strong food safety practices, outbreaks can still happen. If a customer gets sick and your restaurant may be involved, act quickly. Delays can put more people at risk.
Start by contacting your local health department. They’ll investigate the situation and guide your next steps. Notify your staff and any customers who may have eaten affected food during the timeframe in question. Clear communication matters.
Gather as much information as possible, including symptoms, menu items consumed, and when customers ate at your establishment. This helps investigators identify the source and limit further spread.
If you identify a likely cause, remove the affected food immediately and prevent cross-contamination. Then thoroughly sanitize your kitchen, surfaces, utensils, and equipment. Dispose of any potentially contaminated food. When in doubt, throw it out.
After the immediate issue is contained, review your food safety procedures. Updated handling protocols, stronger employee training, improved inspections, and clear sick leave policies can help prevent future outbreaks.
More than just compliance
It’s easy to think of the big six as a compliance requirement, something to cover during certification and move on from. But in practice, they’re a shortcut to understanding where your operation is most exposed.
Food safety isn’t just a matter of reacting to problems after they happen, but creating an environment where those problems have fewer opportunities to start.
Trust20 gives your team the kind of structured training that holds up under real kitchen stressors, not just in theory. When food safety becomes part of how your operation runs, day to day, consistency follows naturally. Explore our training products today!
FAQ
What are the big six foodborne illnesses?
They are six high-risk pathogens identified by the FDA: Norovirus, Salmonella Typhi, nontyphoidal Salmonella, Shigella, Shiga toxin-producing E. coli (STEC), and Hepatitis A. They’re responsible for many of the most serious foodborne illness outbreaks in foodservice.
Why are the six foodborne illnesses treated differently?
The six diseases spread easily, require very little exposure to cause illness, and are often transmitted through infected food handlers rather than just contaminated ingredients.
Which foodborne illness is the most common?
Norovirus is the leading cause of foodborne illness outbreaks in the United States, particularly in restaurants and similar environments.
Am I allowed to work with food while sick?
That depends on the symptoms, but for illnesses associated with the big six, even mild symptoms can be a risk. Clear reporting and exclusion policies are essential to prevent transmission.
Do experienced staff still need training on foodborne illnesses?
Yes. Experience doesn’t eliminate risk, especially in fast-paced or high-risk environments like hospitals or schools. Regular refreshers help you make sure that all your good habits hold up under pressure.
What’s the most effective way to prevent foodborne illnesses?
Focus on consistency in three areas: employee health reporting, proper hand hygiene, and preventing cross-contamination. When those systems are strong, the risk of an outbreak drops significantly.
Sources:
- Food and Drug Administration: 2022 Food Code
- CDC: Estimates of Foodborne Illness in the United States
- CDC: Foodborne Illness Outbreaks at Retail Food Establishments — National Environmental Assessment Reporting System, 25 State and Local Health Departments, 2017–2019
- Centers for Disease Control and Prevention: Norovirus Fact Sheet for Food Workers
- Cleveland Clinic: E. coli: Infection, Causes, Symptoms & Treatment
- World Health Organization: Hepatitis A
- CDC: Guillain-Barré Syndrome | Campylobacter
- L. Hannah Gould et al: Contributing Factors in Restaurant-Associated Foodborne Disease Outbreaks
