By Dr. Danielle Kelvas | Posted On: March 29, 2023

A Complete Guide to Foodborne Illnesses

The CDC estimates that every year, 48 million people in the U.S. contract foodborne illness.  That's one case per year for every 6 Americans.

For some, it's just a bad night hunched over the toilet bowl. For others, it's a lot more serious. Foodborne illness hospitalizes 128,000 Americans every year and kills 3,000 of them. 

But what causes foodborne illness, exactly? What are the most likely sources? Who is most susceptible?

And most importantly to restaurants: how do you prevent foodborne illness?

What is a Foodborne Illness?

It's a broad category. Any disease or period of sickness that comes from contaminated food (or drink, including water) is considered a foodborne illness.

What are the Different Types of Foodborne Illness?

Most foodborne illnesses are foodborne infections caused by pathogens – harmful bacteria, viruses, or parasites seeking out a host so they can reproduce.

If you kill the pathogen before it's consumed, no one gets sick. Foodborne infections usually take longer to kick in than non-infectious illnesses, because the pathogen has to make itself at home before it starts causing damage.

The second most common type of foodborne illness is often called "foodborne intoxication." That doesn't mean the food makes you drunk – in this case, it literally just means "resulting from a toxin."

Foodborne toxins usually come from bacteria or mold living in or on your food. The organism itself doesn't make you sick, but it produces a substance that does. You can kill the organism, but the toxin remains.

Finally, some foodborne illnesses are caused by chemical or heavy metal contamination (which really helps all foodborne illnesses live up to the nickname "food poisoning").


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What are the Symptoms of Foodborne Illness?

Since foodborne illness is a broad category, the symptoms vary heavily by cause.

There are some weirdos. Botulism (a foodborne intoxication) causes muscle weakness or paralysis. Tapeworms (an infectious parasite) cause increased appetite paired with weight loss.

However, the most common symptoms for all types of foodborne illness follow the formula of the "stomach flu." Sometimes after eating contaminated food, you come down with diarrhea, vomiting, and/or stomach cramps (usually within 12-72 hours).

You may get over it in 24 hours, or symptoms can last as long as weeks depending on the bug, like E. coli or cholera.

Why Does Foodborne Illness Present That Way?

There are two reasons that food poisoning usually causes diarrhea and vomiting.

Sometimes these symptoms are defensive. If your body recognizes that you've eaten something harmful, it wants to expel the substance or pathogen as quickly as possible. If the alarm sounds before the small intestine, food goes back up; intruders are fast-tracked down after it enters the small intestine.

This is also why seeing and smelling spoiled food makes you nauseous – your body hopes to put you off eating altogether, but if you don't listen, you're primed to eject the "poison" right away.

Other times, these symptoms are a pathogen's offense. Foodborne pathogens usually stick to doing business where they came in – your digestive tract. They enter there, reproduce there, and then hijack your body's defenses to help them exit there.

Giving you an urgent need to vomit is a great way to ensure you're around other people when you do. Pathogens that cause diarrhea bank on poor bathroom hygiene to let them hitchhike their way to a new friend.

What Are the Main Causes of Foodborne Illness?

Most foodborne illnesses are infectious.

What Are the Most Common Foodborne Infections?

The biggest cause of all foodborne illness is norovirus, which is hard to kill and easy to spread. It accounts for more than half of U.S. food poisoning cases.

After norovirus, most foodborne illnesses are caused by four types of bacteria: Salmonella, Clostridium perfringens, Campylobacter, and Staphylococcus aureus.

What Are the Most Dangerous Foodborne Infections?

Some pathogens are less common to get, but more likely to cause severe illness. Your chances of being hospitalized are high if you're exposed to E. coli, botulinum toxin (produced by Clostridium botulinum), Listeria, or Vibrio.

What Foods Are Most Likely to Give You Food Poisoning?

The CDC's analysis of foodborne illness outbreaks between 1998 and 2008 found that leafy vegetables were the largest culprit.

In fact, produce – including leafy vegetables, root vegetables, sprout vegetables, and vine-stalk vegetables – accounted for almost half of all foodborne illnesses in the study.

However, even though meat and poultry sources caused fewer illnesses, they accounted for more deaths.

Who is Susceptible to Foodborne Illness?

Anyone can come down sick with a foodborne illness, but some people are more likely than others to be exposed or show severe symptoms.

Who is Most Likely to Be Exposed to Foodborne Illness?

Your habits (and those of the society you live in) can increase or decrease the likelihood that you'll be exposed to pathogens, toxins, or chemicals in your food that will make you sick.

Individual factors that increase your risk include:

  • Consuming raw milk (the pasteurization process is designed to kill foodborne pathogens)
  • Consuming foods that have been canned, preserved, or fermented improperly (or eating any of these from damaged containers)
  • Not washing leafy greens and other vegetables intended for raw consumption
  • Eating undercooked meat
  • Feeding honey to an infant

Community factors include:

  • Poor separation of human waste from food and water sources (no sewer system)
  • Weak regulatory mechanisms for food safety and environmental protection

Which Groups Are Most Likely to Be Infected When Exposed to Foodborne Pathogens?

If your immune system is strong, you may be able to fight off a foodborne infection without any symptoms. If you're immunocompromised, it's more likely that even a small number of pathogens will overwhelm your immune system.

Demographically, some groups of people are more likely to get sick with the stomach flu and have a more severe set of symptoms because of their immune status. That includes:

  • Pre-school aged children (5 and under) whose immune systems are still developing
  • Older adults (65 and up) whose immune systems are in decline
  • Pregnant women, whose immune system is altered to protect the fetus
  • Anyone whose immune system is compromised by a disease or medical treatment (HIV, medications)

Public health experts call these Highly Susceptible Populations (HSPs), and the CDC recommends that food service operations that serve HSPs take the most stringent precautions.

Which Groups Are Least Susceptible to Foodborne Illnesses?

Young, healthy adults are the least susceptible to foodborne illness.

This doesn't mean this group can't get sick. Instead, they may end up with very mild symptoms (like an ominously rumbly tummy) or recover quickly from an acute illness.

They're the least likely to end up hospitalized or dead due to foodborne illness.

However, large enough doses of the disease-causing agent (or certain virulent foodborne illnesses) can still land young, healthy adults in the hospital, like Hepatitis A.

How Do Restaurants Prevent Foodborne Illness?

Restaurants play a critical role in spreading or preventing foodborne illness. According to the CDC, 70% of reported norovirus outbreaks can be traced back to food service facilities.

Restaurants need a comprehensive plan to tackle all the different ways foodborne illness can pass through their kitchen – from time and temperature control procedures to practices that prevent cross-contamination. A huge part of this plan is a comprehensive training strategy for all food contact employees and in-depth certification for their managers.

Naturally, the cost and logistics of training are always a concern, but reputable online training can provide the best of all worlds. At Learn2Serve by 360training, we have over 20 years of experience providing online coursework and ANSI-CFP accreditation and regulatory approval in many states.

Start with in-depth food safety training for your managers, like ANSI Food Protection Manager Certification. Then provide effective food handler training for your entire staff, whether local regulations require it.

And while COVID-19 rages and food delivery takes up a chunk of your business, Health and Sanitation Safety Awareness (HASSA) certification can help managers and employees keep up with the special food safety demands of these strange times.

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