Stomach Flu vs. Food Poisoning: Is It Possible to Tell Symptoms Apart?

When you’re suffering through a wicked case of diarrhea, sudden vomiting, or the delightful sensation of both at the same time, it can be difficult to tell if your symptoms might be the result of the stomach flu or food poisoning.

While the stomach flu (also known as a stomach virus or bug) and food poisoning tend to be lumped together into one unpleasant category, there are actually many differences between the two. Still, it’s understandable to get confused, as they can both make your life hell for 48-ish hours.

“Food poisoning and a stomach virus are nearly impossible to tell apart,” Diane Calello, M.D., medical and executive director of the New Jersey Poison Information and Education System and associate professor of emergency medicine at Rutgers New Jersey Medical School, tells SELF. “Sometimes, the only way to know is if you can identify a food only eaten by people who get sick.”

With that in mind, here’s a comprehensive breakdown of stomach flu vs. food poisoning symptoms, the distinct causes of each, the factors that may help you determine which one is behind your sudden misery, and how to feel better ASAP.

What is food poisoning? | What is the stomach flu? | Causes | Food poisoning symptoms | Stomach flu symptoms | Illness duration | Is it contagious? | Key differences | Similar conditions | Treatment | Food poisoning prevention | Stomach flu prevention

Food poisoning (also known as foodborne illness) is an infection or irritation of your digestive tract that you get from having food and drinks that contain illness-inducing pathogens, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

This means your body is rebelling against viruses, bacteria, or other harmful substances in something you ate, Benjamin Chapman, Ph.D., an assistant professor and food-safety extension specialist at North Carolina State University, tells SELF. These pathogens can lurk in a wide variety of foods, but you may also come down with food poisoning after reheating old food or drinking or eating something that has expired (especially dairy).

Food poisoning isn’t a rare thing—about 48 million people in the U.S. have food poisoning each year, per the NIDDK. The illness is usually acute (meaning it comes on hard and fast), and most people get better on their own without treatment.

First, it’s important to know that the stomach flu has no relation to the “regular” flu. Influenza is a highly contagious viral infection that causes fever, muscle aches, fatigue, and respiratory issues. In severe cases, influenza can be life-threatening (seriously, get your flu shot every year).

The stomach flu, on the other hand, is what’s known as viral gastroenteritis, and it happens when a virus causes an infection in your gut, according to the U.S. National Library of Medicine.

When it comes to viruses, norovirus is the most common cause of foodborne illness in the U.S., the Centers for Disease Control and Prevention (CDC) says. It typically hangs out in items like raw, ready-to-eat produce; shellfish; and contaminated water.

On the bacterial side, food poisoning can be set off by salmonella, listeria, shigella, campylobacter, and E. coli, among others, according to the Mayo Clinic. These can show up in anything from hot dogs, milk, egg yolks, alfalfa sprouts, meat, poultry, and beyond.

Food contamination can happen at any point, whether it’s through soil as it’s grown, in a storage facility, or on your countertop when you leave food out for too long, the CDC says. You may also get food poisoning if someone with one of these illness-inducing microorganisms in their system handles your food or utensils.

Norovirus is also one of the most common causes of the stomach flu; it’s actually responsible for up to 21 million viral gastroenteritis infections each year, per the CDC. So, yes, the stomach flu can be a type of food poisoning.

You can pick up viruses that cause the stomach flu by touching a surface that someone with the infection touched or by having direct contact with them. You can also get it through food, though, which brings us to the trippiest part of this entire conversation: You can technically have food poisoning and the stomach flu at the same time.

Let’s say you pick up a case of viral gastroenteritis after a dinner of norovirus-contaminated scallops. That basically means you got the stomach flu from a food-based source. “Is it food poisoning or the stomach flu? There’s not really a clear line you can draw,” Amesh A. Adalja, M.D., board-certified infectious disease physician and senior scholar at the Johns Hopkins Center for Health Security, tells SELF.

So, what does food poisoning feel like? Let’s just say it’s not a great time. No matter the cause, food poisoning can cause intense symptoms. The NIDDK specifically lists these as a possibility:

• Diarrhea or bloody diarrhea
• Vomiting
• Pain in your abdomen
• Fever or chills
• Headache

While it’s not as common, some types of food poisoning like botulism and fish and shellfish poisoning can impact your nervous system, the NIDDK says. That can cause additional symptoms like:

• Blurred vision
• Paralysis
• Tingling or numbness of your skin
• Weakness

Plus, all that vomiting and diarrhea can make it difficult to keep any food or liquids down, potentially leading to dehydration. Pair that with trouble sleeping, and you can end up feeling pretty exhausted, Anita Gorwara, M.D., family medicine physician and medical director of urgent care at Providence Saint John’s Health Center in Santa Monica, California, tells SELF.

These symptoms can come on pretty quickly, but the exact time frame will depend on the food you ate and the type of pathogen you’re dealing with, says Dr. Calello. “Some cause illness quickly after the consumption of poisoned food, such as reheated fried rice. But some can take hours to develop,” Dr. Calello says. Here are a few examples of what you can expect in terms of the onset, per the CDC:

• Salmonella: Between six hours to six days (not a typo!) after exposure
• Norovirus: Between 12 and 48 hours after exposure
• E. coli: Three to four days after exposure
• Listeria: One to four weeks after exposure

The symptoms of the stomach flu usually aren’t all that different from the symptoms of food poisoning (meaning they can also lead to dehydration). According to the Mayo Clinic, you may experience the following, which typically start to appear one to three days after you’ve been infected:

• Watery, usually non-bloody diarrhea
• Abdominal cramps and pain
• Nausea, vomiting, or both
• Occasional muscle aches or headache
• A low-grade fever or chills

“If given the options, I would take three weeks of a cold, cough, and fever over 48 hours of a stomach bug because it can really knock your socks off,” Dr. Gorwana says.

Thankfully, both illnesses are typically short-lived as long as you don’t develop any complications (even if the symptoms make it feel like the longest few days of your life). Most cases of the stomach flu last for less than a week and many people get better on their own without medical intervention, according to the NIDDK. As for food poisoning, you can expect a mild case to last a few hours to several days as well.

Pathogens like salmonella, norovirus, and E. coli can spread from person to person. In fact, if you have a norovirus illness in particular, you could be shedding billions of microscopic particles—and only a few are needed to cause illness, according to the CDC.

A person can eat food that leads to food poisoning or the stomach flu, for example, and then spread these germs around their immediate environment, says Dr. Gowara. You can get sick by having direct contact with the infected person, like through caring for them or sharing eating utensils. In an unpleasant-to-think-about scenario, you may also get sick by touching a surface that is contaminated with the pathogen (say, from the infected person’s puke in the bathroom) and then putting your unwashed fingers in your mouth.

A person is most contagious when they’re experiencing their symptoms at full throttle, especially vomiting, as well as during the first few days when they’re starting to feel a bit better, per the CDC.

There’s a lot of overlap between the symptoms of food poisoning and stomach flu, so you—and your doctor—may need to do a little detective work to try to suss this out. “It’s extremely hard to tell the difference between the two,” Dr. Gorwana says. Mostly, it comes down to the symptoms you’re dealing with. Here are a few key areas to consider:

Remember, the stomach flu typically shows up within one to three days after you’ve been exposed. So, after that, you should start to feel like yourself again, Dr. Adalja says.

If you’re dealing with symptoms for a shorter or longer time than a day or two, you may have food poisoning. While norovirus is a common cause of both food poisoning and the stomach flu, so many pathogens can potentially cause food poisoning that it can have a wider time frame than the stomach flu. Symptoms of food poisoning can crop up just a few hours after contamination, or even days or weeks later, and they can typically last from a few hours to several days, according to the Mayo Clinic.

If you have diarrhea and are brave enough to look into the toilet bowl, take a peek. It’s like the poop version of reading tea leaves: If you see blood in your diarrhea, it could be a sign of food poisoning.

Bloody diarrhea is more likely to be a symptom of some types of food poisoning because some bacteria, like shigella, can cause inflammatory changes in the intestines and lead to bleeding, but viruses are less likely to do so, Dr. Adalja explains. (If you do see blood in your poop, you should let your doctor know.)

Norovirus seems more likely to cause projectile vomiting and stomach cramps in patients than most other pathogens that cause food poisoning or the stomach flu.¹ “The precise mechanism behind norovirus-induced [projectile vomiting] and stomach cramps is unknown but is likely an interaction between the virus and the immune system,” Dr. Adalja says. If needed, your doctor can collect a stool sample to figure out what’s happening and treat you from there.

These illnesses can easily be confused for each other, but they can also be mistaken for any other illness or condition that causes G.I. distress, including COVID-19 since it’s now well known to cause gastrointestinal issues like nausea, vomiting, or diarrhea in some people,² Dr. Calello says.

Food allergies or intolerances can also cause similar symptoms, but they shouldn’t feel “as dramatic” as food poisoning or the stomach flu, Dr. Gorwara says. An issue with dairy or gluten, for example, is “usually more diarrhea than vomiting and never associated with a fever,” she says.

Basic treatment for food poisoning and the stomach flu is the same, but if you have a severe case of either, you might need to see a doctor. For both, the most important thing is to keep yourself hydrated, Dr. Adalja says, as the vomiting, diarrhea, and inability to eat or drink much can zap much-needed liquids from your body.

While water is great, an electrolyte solution like Pedialyte, fruit juice, or broth can help replace nutrients and electrolytes you’ve lost, if you can handle it. Just do your best—even doctors admit that “it’s hard to stay hydrated when you’re feeling that crappy,” Dr. Gorwana says.

It’s also smart to take it easy on the food front. “Be gentle to your stomach,” Dr. Calello says. “Eat bland food—nothing fried, sweet, or spicy. Once you can tolerate clear liquids and bland food, you can start to add more flavors back into your diet.”

You should also check in with your doctor before you self-treat with over-the-counter drugs. “OTC diarrhea medications can be helpful, but can also prolong food poisoning cases,” Dr. Calello says, “so it’s important to only take them when needed.”

Again, these illnesses typically pass with a lot of suffering but minimal complications. However, there are some signs that you need medical attention, according to the Mayo Clinic:

• You’ve been vomiting frequently and unable to keep liquids down for more than 24 hours.
• You see blood in your vomit or poop.
• You have severe abdominal pain.
• You have diarrhea for three or more days.
• You experience signs of dehydration like excessive thirst, dry mouth, dizziness, and dark yellow pee.
• You have a fever.
• You experience any neurological issues like blurry vision, muscle weakness, or tingling in your arms (campylobacter, a common cause of food poisoning, is also a risk factor for the rare autoimmune illness Guillain-Barré syndrome, which affects the neurological system by damaging nerves, the CDC says).

Depending on what you’re dealing with, treatment might range from antibiotics if necessary to anti-nausea medications. (Important to note: Antibiotics help some bacterial G.I. infections, but won’t do anything to kill a stomach virus, per the NIDDK.) If you’re dehydrated, you’ll be given fluids through an IV to ensure your body can continue its necessary functions, Dr. Gorwara says.

Once you’re done puking, you’ll probably want to avoid the experience again—and being on top of your hygiene is the first step. That means washing your hands well, especially around food, and if you have kids, making sure they’re washing their hands well too. Here are a few other precautions you can take to prevent food poisoning, according to the U.S. Department of Health & Human Services:

• Keep raw and ready-to-eat food separate.
• Cook foods to the recommended temperatures.
• Refrigerate or freeze food within one to two hours of cooking or buying it.
• Avoid thawing food at room temperature.
• Throw out any food you’re not sure about. If you’re even a bit hesitant, research the shelf life of that food so you know when it’s no longer good. Avoid just reheating leftovers repeatedly—that doesn’t extend their shelf life (and can make the quality worse, too, per the U.S. Department of Agriculture).

The Mayo Clinic recommends following a few key steps to prevent the stomach flu:

• If you’ve recently come into contact with someone who has the stomach flu or if someone in your home has it, disinfect surfaces as often as possible.
• Avoid getting too close to someone who has the virus.
• Avoiding sharing things like utensils, drinking glasses, plates, and towels.
• Make sure your kids are vaccinated against rotavirus, which most typically causes the stomach flu in children (there’s unfortunately no norovirus vaccine for adults, though).
• When traveling, drink bottled water and avoid ice cubes (both may be contaminated) and be wary of raw food and undercooked meat and fish.
• Finally, make sure you follow food safety recommendations, like washing your hands after you use the bathroom and before you eat.

Bottom line: Yes, it hurts to toss out that delicious sandwich you forgot to pop in the fridge. But getting food poisoning or the stomach flu hurts a whole lot more. If you’ve set up shop in your bathroom and notice any of the severe symptoms mentioned above, don’t hesitate to call your doctor to figure out the next best steps. Dr. Gorwana also offers up this reassurance, for what it’s worth: “Just take it easy as best as you can. It’s usually over within 48 hours.”

Sources:

1. Journal of Clinical Microbiology, Advances in Laboratory Methods for Detection and Typing of Norovirus
2. The Ochsner Journal, Gastrointestinal Manifestations of COVID-19: A Review of What We Know

Related:

• 12 Things That Can Cause Bizarre Green Poop
• How to Wash Fruit and Vegetables So They’re as Clean as Possible
• Should You Be Washing Chicken Before You Cook It?