Stomach flu vs food poisoning

Both stomach flu and food poisoning are common illnesses with similar symptoms. However, both of them have the potential to make you very sick. In the last 15 years, I have treated several patients hospitalized with stomach flu and several others with food poisoning. It is possible to distinguish between the two if you pay close attention to the symptoms.

I am writing this article based on my personal experience as well as a review of relevant medical literature.

In this article, I will compare and contrast stomach flu with food poisoning to help you distinguish between the two. I will also describe when you may need hospitalization with stomach flu or food poisoning, and what you can expect during hospitalization.

Comparing stomach flu and food poisoning

Let’s look at this table that compares and contrasts stomach flu with food poisoning:

Stomach FluFood Poisoning
Medical nameAcute viral gastroenteritisToxin-mediated food poisoning
Caused byViruses such as Norovirus and RotavirusToxins formed by bacteria such as Bacillus cereus or Staphylococcus
Nausea and vomitingUsually less severe and less common than diarrheaMore common than diarrhea and more severe
DiarrheaDiarrhea is the most prominent symptomLess common, but may be severe when present
When do symptoms start?Usually at least 2 days after eating infected foodStarts much faster than stomach flu; earliest: 1hr, latest: 16 hrs
How long do the symptoms last?2 to 3 daysUsually resolves within 24 hours
Belly painCramp-like belly pain associated with diarrheaBelly cramps could be really bad
FeverMaybe presentUsually absent
Cough, sore throat, or runny noseMaybe presentUsually absent
Commonly seen in1. Cruise ships
2. Unsanitary buffet meals
3. Large catering events
4. Travellers
Reheated leftover food that may have been contaminated or left out in room temperature for too long
Stomach flu vs food poisoning
A diagram that shows how stomach flu and food poisoning occur to identify differences between the two
A diagram that shows the differences between stomach flu and food poisoning

Overall, food poisoning happens much faster than stomach flu, and resolves faster too. With food poisoning, the toxins are already in the food. Bacteria consumes the food and makes the toxins long before you eat it. The toxin starts working as soon as it is absorbed in your stomach.

On the other hand, the stomach flu virus doesn’t spoil the food. Food will taste, smell, and feel normal when you eat it. The virus is not active until it gets inside your body. It needs time to invade your cells and use your protein to multiply its genetic material.

When do you need hospitalization for stomach flu or food poisoning?

Most of the time, food poisoning or stomach flu doesn’t need hospitalization. If you are relatively young and healthy, you can stay home and wait for things to get better, as they will get better within a few days. You can try to keep yourself hydrated by drinking sports drinks, broth, or special electrolyte replacement products that can be bought at the pharmacy. The goal is to replace fluids and electrolytes lost from vomiting and diarrhea.

You need watch for things getting worse. If you have any of the following, you need to get immediate medical attention, possibly requiring hospitalization:

  1. Feeling dizzy and lightheaded when standing
  2. Unable to keep any drink down due to persistent vomiting
  3. Too weak to stand up and walk
  4. Severe intolerable belly cramps
  5. Having diabetes and your blood sugars are too high or too low
  6. Rapid heart rate
  7. Low blood pressure

What to expect when hospitalized for stomach flu or food poisoning

Hospitalization for stomach flu or food poisoning is usually limited to 24 to 48 hours, unless you have other medical problems complicating your hospital stay.

Here are a few things you can expect to get when hospitalized:

  1. IV fluids: The most common reason you may need hospitalization in these situations is severe dehydration. When you are unable to keep food or drink down, the only way to keep you hydrated is by giving you fluids and electrolytes through your veins.
  2. Vital signs: You need frequent monitoring of your vitals to make sure your heart rate and blood pressure are going in the right direction.
  3. Close monitoring of electrolytes: Electrolytes are the charged particles in your blood that are essential in most of electrical activity in your body, such as nerve conduction, heart beat rhythm, or muscle contraction. Examples of electrolytes include sodium, potassium, calcium, and magnesium. You may lose electrolytes with vomiting and diarrhea. When your dehydration is severe enough to result in hospitalization, your electrolytes may be imbalanced. You may need frequent blood tests to check your electrolytes.
  4. Following kidney function: Severe dehydration may cause a temporary shutdown of your kidneys. Your kidney function needs to be followed closely with frequent blood tests.
  5. Controlling your nausea: You may not be able start eating or drinking unless your nausea improves. IV medications may be given to help improve your nausea so that you can start drinking fluids.
  6. Frequent blood sugar checks: If you have a history of diabetes, your blood sugar needs to checked frequently to make sure it isn’t too high or too low.
  7. Feeding trials: After controlling your nausea, the nurses will try to feed you as much as they can. They will start with a clear, liquid diet to make sure you keep your food down. Gradually, your food and drink intake will improve. When you are able to eat and drink enough to not require IV fluids, you will be discharged home.

In conclusion, stomach flu and food poisoning may have similar symptoms, but you can distinguish between the two if you pay close attention. You may need short hospitalization for either of them if you develop severe dehydration or electrolyte abnormalities.