About one in six people in the United States experience foodborne illness each year. Many cases can be traced to common kitchen mistakes, such as undercooking food, leaving it out too long, and not washing produce before eating it or storing it.

While most microbes are harmless, some can cause serious illness.

“The most common foodborne illnesses are due to bacteria, but they can also be caused by parasites and viruses,” says Michael P. Angarone, DO, an Infectious Disease doctor at Northwestern Medicine. “You can contract them by eating food contaminated at its source or during food preparation.”

Fortunately, many cases are preventable. Learning how to safely cook food, store it and handle it can go a long way in preventing foodborne illnesses.

What Causes Foodborne Illness?

Harmful bacteria grow quickly in the “danger zone,” which is between 40 and 140 degrees Fahrenheit. Foodborne illness can develop when food remains in this temperature range for too long.

To help keep food out of the danger zone:

• Keep hot food at or above 140 degrees Fahrenheit.
• Keep cold food at or below 40 degrees Fahrenheit.

Foodborne illness can occur when:

• Food is not cooked to a safe internal temperature
• Food is left at room temperature too long
• Cross-contamination occurs between foods
• Fresh produce is not washed before eating it
• Hands, surfaces or utensils are not cleaned properly

Common Types of Foodborne Illnesses

Some foodborne illnesses are more common than others. Here are some you may have heard of:

Bacterial illnesses

• Salmonellosis is caused by Salmonella bacteria and often linked to raw or undercooked poultry, eggs and produce. Symptoms may include diarrhea, fever and stomach cramps.
• E. coli infection is caused by Escherichia coli bacteria and commonly associated with undercooked ground beef, leafy greens and contaminated water. Some strains can cause severe illness.
• Listeriosis is caused by Listeria monocytogenes and most often linked to deli meats, soft cheeses and other refrigerated foods. It can be especially dangerous during pregnancy.
• Campylobacter infection is often linked to raw or undercooked poultry and unpasteurized milk. Symptoms may include diarrhea, fever and stomach cramps.

Viral illnesses

• Norovirus is a highly contagious virus that can spread through contaminated food, water, surfaces or direct contact with a person who has norovirus. It often causes vomiting and diarrhea.

Parasitic illnesses

• Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis, often linked to contaminated fresh produce, including berries and leafy greens. Symptoms may include diarrhea, loss of appetite, fatigue and stomach cramps.
• Giardiasis is caused by the Giardia parasite and often spreads through contaminated food or water. Symptoms may include diarrhea, gas and stomach cramps.

Is Foodborne Illness Contagious?

Some foodborne illnesses can spread from person to person, while others are primarily spread through contaminated food or drinks.

For example, norovirus spreads easily from person to person, as well as through contaminated food or surfaces.

If you’re sick, wash your hands frequently and avoid preparing food for others until your symptoms have completely resolved.

What Symptoms Should You Watch For?

Symptoms of foodborne illness can vary, but common signs include:

• Nausea
• Vomiting
• Diarrhea
• Stomach pain
• Fever

Symptoms often begin within hours after eating contaminated food, but sometimes they can take a couple of days to appear. Most cases improve within one to two days, but more severe symptoms may require medical care.

When Should You See a Doctor?

Although most foodborne illnesses are mild, some require attention.

Seek medical care if you have:

• Symptoms for more than a few days
• A high fever (102 degrees Fahrenheit or higher)
• Bloody diarrhea
• An inability to keep fluids down or signs of dehydration

These can indicate a more serious infection and should be evaluated by a doctor.

Who Is at Higher Risk for Foodborne Illnesses?

Certain groups are more likely to experience severe illness from contaminated food, including:

• Young children
• Older adults
• People who are pregnant
• People with weakened immune systems

For these groups, taking extra care with food safety is especially important.

Which Foods Are High Risk?

Some foods are more likely to carry bacteria when not properly handled or cooked, including:

• Unwashed fruits and vegetables
• Raw meat, poultry and seafood
• Eggs
• Unpasteurized dairy products
• Refrigerated ready-to-eat food that has not been properly stored, such as bags of salad and berries

Improperly handled perishable food, especially food left out at room temperature, can quickly become unsafe.

How to Safely Handle and Prepare Food

Taking simple steps in the kitchen can help protect your health.

Clean

Always wash your hands with warm, soapy water before and after handling food. Also, wash countertops, utensils and cutting boards regularly.

“Make sure to wash and dry all produce, including leafy greens, before eating it,” says Dr. Angarone.

Separate

To avoid cross-contamination, keep raw foods separate from cooked and ready-to-eat foods. Use separate cutting boards when handling raw meat, poultry and seafood.

Cook

Always cook food to the proper safe internal temperature. Use a food thermometer instead of relying on color or appearance.

Temperature guidelines for cooking:

• Chicken and turkey: 165 degrees Fahrenheit
• Ground meats like beef and pork: 160 degrees Fahrenheit
• Steaks, roasts and fish: 145 degrees Fahrenheit
• Leftovers: 165 degrees Fahrenheit

Chill

Store food in the refrigerator promptly. Refrigerate leftovers within two hours of cooking or serving.

Keeping perishable food cold slows the growth of harmful bacteria and helps keep food out of the danger zone.

“The most effective way to avoid foodborne illness from produce that will be eaten uncooked is to thoroughly wash, dry and store it in the refrigerator,” says Dr. Angarone.

How Long Can Food Sit Out?

Many cases of foodborne illness begin when food remains in the danger zone for too long.

Perishable food should not sit out for more than:

• Two hours at room temperature
• One hour when outdoor temperatures exceed 90 degrees Fahrenheit

Throw away any food that has been left out longer than recommended.

Food Safety Starts at the Grocery Store

Food safety begins before food reaches your kitchen. When grocery shopping, pick up refrigerated and frozen items last and head home promptly. Avoid leaving groceries in a hot car for extended periods, especially during warmer weather.

Consider placing meat, poultry and seafood in separate bags to help prevent cross-contamination while transporting groceries.

Common Food Safety Misconceptions

Many cases of foodborne illness can be traced back to common food safety myths. Understanding what’s true and what’s not can help reduce your risk.

Myth: If food looks and smells fine, it’s safe to eat.
Fact: Harmful bacteria aren’t always visible, and contaminated food may not smell or look different.

Myth: Leaving food out for a short time is OK.
Fact: Bacteria can grow quickly at room temperature, especially when food remains in the danger zone.

Myth: You should always wash raw meat to remove bacteria.
Fact: Instead of washing raw meat, the U.S. Department of Agriculture (USDA) recommends cooking it to a safe internal temperature to get rid of harmful bacteria.

Myth: You can tell when food is fully cooked by looking at it.
Fact: The only reliable way to know whether food has reached a safe internal temperature is to use a food thermometer.