Is Food Poisoning Contagious? Causes and Prevention

Food poisoning is a catch-all term for more than 250 different foodborne diseases.

Nearly 48 million people contract a foodborne disease every year in the United States.

If you’re one of them, you may be suffering from stomach cramps, vomiting, diarrhea, or feeling dehydrated. Rarely, certain cases of food poisoning can even be life-threatening.

But if you have food poisoning, are you contagious?

It depends on the cause of your food poisoning.

In this article, I’ll talk about the symptoms of food poisoning, the different causes of food poisoning, and whether they are contagious.

I’ll also outline some precautions you can take to keep yourself and others from becoming sick. And I’ll tell you when to seek medical treatment.

Is Food Poisoning Contagious?

Most types of food poisoning are not contagious.

But there are a few types of foodborne illnesses that can be passed from person to person, or even from animal to person.

Many foodborne illnesses also share similar symptoms with bacterial or viral infections that can be very contagious. 

What Causes Food Poisoning?

Food poisoning is fairly common, but it’s a catch-all name for hundreds of foodborne illnesses. Not every case is the same. 

Food poisoning from bacteria

Food can become contaminated with a bacteria that survives ingestion and continues multiplying in the stomach.

The bacteria produces toxins that can cause severe illness and even be life-threatening. 

Food poisoning from viruses

Viruses can live in and on food, and be transmitted to humans.

Viral foodborne illnesses are the most common, and are very contagious. Like bacterial infections, these can be very dangerous for people with weak immune systems. 

Food poisoning from parasites

Parasites, while less common than viruses and bacteria as a cause of food poisoning, can also live in food or water and be consumed, causing upset stomach and other symptoms, including nausea, vomiting, and diarrhea.

Symptoms of a parasitic infection can take longer to develop and recover from.

Symptoms of Food Poisoning

Food poisoning symptoms can begin as soon as a few hours after consuming contaminated food, or up to several weeks later.

Most people notice symptoms within the first day or two.

The most common symptoms include:

• Nausea and/or vomiting and loss of appetite
• Diarrhea, which can be explosive or watery, and may contain blood or mucus
• Abdominal pain and stomach cramping 
• Weakness and fatigue
• Fever
• Muscle aches over the entire body
• Chills and shakes

Dehydration can happen quickly, especially if you are both vomiting and having diarrhea.

Staying hydrated as much as possible is critical, and if you develop symptoms of dehydration, it’s important to seek medical attention right away.

Common Causes of Food Poisoning

The most common causes of food poisoning include:

E. coli

While Escherichia coli bacteria are a normal part of your gut bacteria, certain species of E. coli can cause disease.

These can be found in contaminated water or foods such as insufficiently cooked meat, unpasteurized milk, unwashed lettuce, or raw sprouts.

Consistent handwashing and thorough cooking or pasteurization of food and liquids can help prevent E. coli outbreaks.

Listeria

Listeria monocytogenes is one of the rarer causes of food poisoning, but can be deadly—more than 250 people die from listeriosis, the infection caused by listeria, each year.

Insufficiently chilled perishable foods, unpasteurized milk and cheese, and prepared deli meats are the most common carriers of L. monocytogenes bacteria.

Pregnant women, young children, and people with weak immune systems are at especially high risk.  

Norovirus

Norovirus is the most common cause of food poisoning in the U.S, and norovirus gastroenteritis is extremely contagious.

A norovirus-related illness or outbreak is usually easy to recognize, with a sudden appearance of symptoms as soon as 12 hours after exposure or ingestion, followed by projectile vomiting, diarrhea and cramps.

Norovirus can spread quickly through a home, child care center, cruise ship, or nursing care facility. 

Salmonella 

Salmonella infection symptoms can start as soon as six hours after exposure to contaminated food or water.

In the U.S., victims of the bacteria usually suffer from nausea, vomiting, diarrhea, cramps, and fever lasting from a few days to a week. 

Travelers outside the U.S. are at higher risk of developing enteric fever (including typhoid fever) with more severe symptoms including high fever, diarrhea or constipation, aches, headache, and drowsiness.

Salmonella can be found in many foods, including unwashed fruits and vegetables, meat, and unpasteurized dairy, poultry and eggs.

You can also get Salmonella from certain animals, including reptiles and poultry. 

Cholera 

Vibrio cholerae bacteria causes cholera in people who drink contaminated water or eat food that contains the bacteria. 

Many infections are mild and cause almost no symptoms, but one in 10 patients experience more serious infections causing vomiting, “rice water” diarrhea, leg cramps, and in severe cases, restlessness or irritability.

The real danger of cholera is dehydration, which can happen quickly and lead to kidney failure and death. 

Bacillus cereus

Bacillus cereus is a bacteria in the form of a cold and heat resistant spore, which means that refrigerating food may not stop it from multiplying, and reheating food may not kill it.

The bacteria is found in soil, and is commonly present in foods like rice, which may have tiny amounts of soil contamination after processing. 

Small amounts of bacteria can survive the cooking process, and then multiply while leftovers are in the fridge, reaching levels that can cause diarrhea or vomiting.

The best way to avoid B. cereus food poisoning is to only cook as much rice as you need, and discard any leftovers.  

Campylobacter 

Campylobacter is one of the most common bacterial causes of diarrheal illness in the U.S., and the one most commonly diagnosed in travelers returning to the U.S. from abroad.

Common culprits are contaminated water, unpasteurized milk or cheese, and raw or undercooked poultry, meat, or seafood.

Campylobacter can also be harbored by many common pets who may transmit the disease, so make sure to practice good hygiene around animals, as well as in the kitchen. 

Shigella 

Shigella bacteria cause an infection called shigellosis, which causes diarrhea (sometimes bloody), fever, and stomach cramps.

People with underlying conditions, severe illness, or weak immune systems are at higher risk for severe complications. 

Botulism

Most people have heard of botulism, but cases are extremely rare, since Clostridium botulinum bacteria survive inside of spores, which usually act as a protective coating.

However, under the right conditions, spores can multiply and produce toxins, causing infection. Most cases of botulism are traced back to canned or jarred food that was improperly sealed.

Always throw away bulged cans or jars, and be careful with fermented foods.

Hepatitis A

Hepatitis A, or Hep A, causes inflammation of the liver, leading to debilitating food poisoning symptoms, and in severe cases, dark urine and yellowing skin, which can be signs of liver failure.

The hepatitis A virus can be ingested via contaminated food or water, or it can be transmitted directly from one person to another, making it another contagious form of food poisoning.

Unlike other forms of food poisoning, there is a safe, effective vaccine for Hep A, which is often mandated for food workers and recommended when traveling abroad. 

Treatments and Prevention

Treatment for most types of food poisoning centers around staying hydrated and decreasing nausea, vomiting, diarrhea, and abdominal cramping.

Viral infections are never treated with antibiotics, as they are not effective for viral infections.

While most bacterial infections also resolve on their own, for certain severe bacterial infections, antibiotics may shorten the duration of symptoms.

Parasitic infections almost always require anti-parasitic medication.

While most people can be safely treated at home, individuals who are at particularly high risk of developing severe illness or becoming easily dehydrated, including young children, the elderly, pregnant women, and those with weak immune systems should always be evaluated by a doctor if they become ill. 

The best way to prevent food poisoning is to handle food carefully. Keep perishables cold.

Cook meat, poultry, and seafood thoroughly. Wash all fruits and vegetables to remove surface contaminants.

Stick to pasteurized cheeses, milks, and juices. Always keep cooked and raw meat separate to avoid cross-contamination, and refrigerate leftovers promptly.

Wash your hands frequently, and wear a face mask when doing food preparation in crowded facilities.  

If you plan to travel outside of the U.S., talk to your doctor about any needed vaccinations to prevent catching food poisoning, as well as what to bring with you in case you do develop symptoms.

If you are going to a picnic, party, or reunion, be wary of high-risk foods that aren’t refrigerated for hours at a time.

These high-risk foods include anything with eggs, mayonnaise, poultry, seafood, meat, or unpasteurized cheese. Avoid fruit and vegetable salads if you aren’t sure the produce was washed appropriately. 

Pay attention to how food is prepared, whether you are at your favorite restaurant or planning a trip on a cruise ship, where food poisoning can be a common complaint.

If you see a food prep worker using a cutting board for raw meat, then another type of food, that’s a red flag. Your digestive system won’t thank you for being polite and eating anyway.

Vigilance is your best safeguard against food-borne illness. 

When to See a Doctor

If you have acute food poisoning with non-stop vomiting or diarrhea, you can quickly become dehydrated, and this is especially true for young children, pregnant women, the elderly and those with compromised immune systems and multiple chronic illnesses.

If you become severely dehydrated, you may need IV fluids or other treatment to get better. 

If you have blood in your stool, a fever, or your eyes or skin turn yellow, see a doctor right away.

Always tell your doctor if you have traveled recently, taken any antibiotics or other medications, or have any serious medical conditions. 

How K Health Can Help

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Check your symptoms, explore conditions and treatments, and if needed, text with a healthcare provider in minutes. 

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