Food Poisoning or Stomach Flu: How to Tell the Difference

The causes of stomach flu and food poisoning are totally different. One is caused by a virus, while the other is caused by bacteria or their toxins.
Food Poisoning or Stomach Flu: How to Tell the Difference
Saúl Sánchez Arias

Written and verified by the nutritionist Saúl Sánchez Arias.

Last update: 30 September, 2023

Food poisoning and stomach flu have a number of similarities, but also several differences that must be taken into account. Different treatment is required, depending on the cause of the illness, and that’s why it’s important to make a correct diagnosis.

We’re going to show you the differences between the two conditions, not only regarding their causes, but also their consequences and prognosis. Keep in mind that, in many cases, you will need a doctor’s advice – otherwise, the person’s health could be at risk.

What causes stomach flu?

Stomach flu is usually caused by a virus that causes an inflammation of the digestive tract, which causes problems at the stomach and intestinal level. It’s common to experience vomiting, diarrhea and pain from this kind of infectious pathology.

It should be noted that it’s a contagious disease that can be transmitted between people in close contact. It’s transported by means of the microdroplets that are expelled when speaking. It’s also possible to experience infection through the use of contaminated objects.

Several viruses can trigger the problem. Noroviruses often affect younger children, as do rotaviruses. This is evidenced by a study published in the journal Praxis. However, in adults, astroviruses and adenoviruses are much more common. Some types of coronaviruses may also cause these processes.

Stomach flu viruses.
The viruses that cause stomach flu are very diverse, ranging from rotaviruses to some types of coronaviruses.

Symptoms of stomach flu

Stomach flu usually causes abdominal pain, diarrhea, and vomiting. However, it’s relatively common for these complaints to be accompanied by chills and fever in an attempt by the body to kill the virus causing the illness. In addition, it’s common to experience muscle pain.

What must be closely monitored are the symptoms of dehydration. Sometimes the patient is unable to ingest liquids without vomiting, and is therefore prone to suffer a water deficit. Keep in mind that dehydration can be seriously life-threatening, so watch for associated symptoms.

What causes food poisoning?

Unlike stomach flu, food poisoning is caused by a bacterium or protozoan. The origin is a microorganism or its toxin that irritates and inflames the mucous membranes of the digestive tract and generates, in many situations, a symptomatology similar to the one described.

The most frequent intoxication is caused by bacteria of the genus Clostridium. However, the Salmonella microorganism is also very often responsible for this condition.

According to a study published in the journal Przeglad Epidemiologiczny, the number of cases affected by this bacterium has increased in recent years. It’s found mainly in meats and meat products.

Frequent symptoms

The symptoms caused by food poisoning are very similar to those of stomach flu in certain cases. Diarrhea, vomiting, abdominal pain, fever and dehydration are common. However, these don’t usually last as long, although it will depend on the severity of the poisoning and the amount of bacteria or toxins ingested.

However, some poisonings can cause other organs to fail. The liver is usually the main affected organ. It suffers mainly when mycotoxins from mushrooms are consumed. It has even been shown that these toxins are capable of increasing the risk of cancer and hepatitis.

When to go to the doctor?

Whatever the cause of the discomfort, it’s important to go to the doctor when the symptoms don’t stop within 24 hours or when they worsen over time. This is also the case if you suffer skin alterations, headaches, or intense fever.

In addition, the specialist will be able to offer solutions to cut continuous vomiting in the form of drugs inoculated intramuscularly. These are usually very effective in helping the body to begin to tolerate liquids and reduce the risk of dehydration.

If you experience loss of consciousness or severe pain, you (or someone else) should contact the emergency department immediately.

The symptoms of stomach flu and food poisoning don’t usually last more than 2 days. However, complications can arise at the digestive level, so you need to monitor whether blood appears in the stools and consult a doctor if it does.

How are they diagnosed?

¿Cómo diferenciar una intoxicación alimentaria de la gripe estomacal?
The doctor will ask about the food consumed to determine if there’s a microbiological risk.

To establish the diagnosis of food poisoning or stomach flu, a fairly complete medical history will be necessary. The specialist will ask about the food consumed in the last few hours, to assess whether any of them could have microbiological risk.

Also, it will be necessary to know if any person in close contact is in the same situation. In general, diagnostic tests as such aren’t usually performed, except in the most serious cases. A serology or stool culture may even be requested to know precisely which microorganism is causing the damage.

The recommended treatments, regardless of the reason that causes the pathology, will be aimed at seeking a remission of symptoms, as well as preventing dehydration.

The first thing will be to increase the volume of water gradually, as long as this doesn’t cause nausea or a vomiting reflex. From this point on, easily digestible solid foods, such as white rice and chicken, should be included in the diet. Those products with high fat or fiber content will be the last to be reintroduced.

The most severe cases may require the administration of an antiemetic that cuts vomiting. Intravenous fluids may even be given if symptoms of dehydration develop, although this is a matter for hospital management.

In the case of a viral problem, a vitamin C supplement may be included to strengthen the immune system. If the disease is caused by bacteria or a toxin, some drugs that block its effects or eliminate the pathogen could also be considered. An example would be antibiotics in the most severe cases.

How to prevent them?

Prevention is a key point when it comes to preventing stomach flu and food poisoning. To prevent food poisoning, it’s essential to ensure good hand hygiene and proper food handling before and during consumption. Respecting the cold chain and good storage practices will be essential.

Similarly, not maintaining close contact with those who have developed gastrointestinal symptoms can also prevent you from contracting the disease caused by the virus, if this is the cause.

However, this is quite difficult to do, since these microorganisms are usually very contagious before symptoms appear in people.

Stomach flu and food poisoning: two different problems with similar symptoms

As you have seen, stomach flu and food poisoning share a number of similarities in terms of the symptoms they generate. However, they’re caused by different microorganisms, so the treatment proposed for the most intense forms of the disease are also different.

It’s best to go for prevention and ensure that hygiene measures are followed between people and with food handling. Once the first symptoms have appeared, it’s important to know when to go to the doctor and how to prevent dehydration.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Zbinden A. Virale Gastroenteritis: Es muss nicht immer Norovirus sein [Acute Viral Gastroenteritis: Viruses Other Than Norovirus]. Praxis (Bern 1994). 2019;108(5):335-339.
  • Polański P, Radziszewski F, Księżak E, Wiktor A, Sadkowska-Todys M. Foodborne infections and intoxications in Poland in 2017. Przegl Epidemiol. 2019;73(4):451-462.
  • Marchese S, Polo A, Ariano A, Velotto S, Costantini S, Severino L. Aflatoxin B1 and M1: Biological Properties and Their Involvement in Cancer Development. Toxins (Basel). 2018 May 24;10(6):214.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.