Gastroenteritis: understand the causes and treatments

Diarrhea , vomiting, malaise. All of this after a little food that didn’t go very well. Or maybe it’s your son who, after a long day of playing, now has these symptoms.

You may be dealing with gastroenteritis, an infectious disease that can be dangerous.


What is gastroenteritis?

Gastroenteritis is an inflammation that affects the small intestine and stomach. Although it has nothing to do with the flu , it is sometimes called intestinal flu.

It is caused by an infection that can be viral, fungal or bacterial, but the most frequent is that the causative agent is a virus.

An inflammation is the body’s reaction to tissue damage or infection. The affected area becomes red, hot, with an increased flow of blood and is often painful.

Cells of the immune system are sent to the region for their protection and the body begins to regenerate.

Depending on the region affected and the intensity, an inflammation can cause various symptoms, ranging from headaches and fevers to vomiting and diarrhea.

Gastroenteritis is a case of inflammation that may or may not be caused by an external agent.

This is one of the most common diseases in the world, affecting millions of people multiple times and causing countless deaths annually.

Children under the age of two in some countries may develop gastroenteritis six times or more in a single year. This causes the number of annual infections of the disease to reach more than 2 billion, counting the repetitions.

The disease is more rare in adults as the immune system is usually more developed, but it can also affect them.

The ICD-10 code for gastroenteritis is K52 .


Gastroenteritis can be divided into a few different types. Among them are:

Viral gastroenteritis

Viral gastroenteritis is the most common, often affecting children. It is caused by infection by viruses that affect the digestive system. The most common cause of this type of gastroenteritis is rotavirus .

Bacterial gastroenteritis

Bacterial gastroenteritis is caused by bacteria. This type is more common in adults than the viral form because, in this stage of life, people have usually developed immunity to the main viral infections that cause gastroenteritis.

It is usually contracted through contaminated food, often by E. coli , although this is not the only bacteria capable of causing the disease.

Read more: How bacteria can be fought by the body

Hemorrhagic gastroenteritis

The main characteristic of hemorrhagic gastroenteritis is bleeding from the intestine. In humans, it is usually caused by the bacterial form, specifically because of the E. coli bacteria .

This type of the disease is usually more common in dogs. Canine hemorrhagic gastroenteritis can be caused by parvovirus , infectious hepatitis, coronavirus, distemper and other diseases that can affect the animal.

It is not limited to bacterial or viral infections, but can also be started by parasites.

Eosinophilic gastroenteritis

The eosinophilic version of gastroenteritis is rare, being defined by the penetration of eosinophilic cells into the intestinal tissue.

These cells are part of the immune system and are usually present in the intestinal mucosa, but usually, when it is in deeper tissue, it indicates a disease.

The immune cell causes inflammation, which is normal if there is a bacterium or virus, but in the case of eosinophilic gastroenteritis there is no infection.

Causes of gastroenteritis

Gastroenteritis is caused by an infection that affects the stomach and small intestine. The causative agents are mainly viruses, but bacteria and fungi, in addition to parasites, also have the ability to cause gastroenteritis.

There are some cases where it can be caused even without an infectious agent, but this is rare.

In most cases, gastroenteritis is caused by the following agents:


Rotaviruses, noroviruses, adenoviruses and astroviruses are the types of viruses capable of causing gastroenteritis, each with several different species.

Viruses are responsible for 70% of gastroenteritis cases, with 8 different rotavirus species being the main causes of the disease in children.

It is believed that almost all children aged 5 have already been exposed to rotavirus at least once.

Noroviruses are the most frequent cause of gastroenteritis in adults, as normally a person acquires immunity to rotavirus during childhood.


Second among the main responsible for gastroenteritis are bacteria. In this group, the most common of the agents that cause the disease are Campylobacter .

However, it is common for other bacteria to also lead to an inflammatory reaction of the digestive system, such as:

  • Salmonella (causa salmonelose);
  • Shigella (which causes human shigellosis);
  • Escherichia coli (which can cause various diseases, from food poisoning and appendicitis).


Some parasites are capable of causing inflammation of the stomach and small intestine. This is the case of giardia , a protozoan that establishes in the duodenum, the beginning of the small intestine, and can cause gastroenteritis.

Non-infectious causes

There are numerous causes not directly related to microorganisms. Gastroenteritis is an intestinal inflammation that can be caused by lactose intolerance , gluten intolerance , Crohn’s disease , non-steroidal anti-inflammatory drugs and even various toxins.

Gastroenteritis is a disease with several causes that can vary from toxic to infectious or, simply, an exaggerated reaction of the organism.

Infant gastroenteritis

Children are most affected by gastroenteritis. Especially in developing countries, there are cases of reinfection several times a year.

The main causes of gastroenteritis are viruses, mainly rotaviruses. Normally, after exposure, the immune system gains resistance. This means that the same virus is not able to cause the disease again.

Children have not yet been exposed to as many viruses as an adult, which means they are much more vulnerable. That is why most cases of gastroenteritis affect children.

Care methods for children, as well as symptoms, are the same as for adults.

Hydration and rest are essential. If the child is less than 2 years old, breastfeeding is important and taking it to the doctor is recommended.

Read more: Infections in childhood may increase the risk of mental disorders

Transmission of gastroenteritis

As the agents that cause gastroenteritis are numerous, the transmission of the disease occurs in several ways. Between them:

Contaminated water

Contaminated water is one of the main ways of transmission of gastroenteritis since several microorganisms that cause the disease can live in the water. Parasites and bacteria can come into contact with humans in this way.

A food washed with contaminated water can also cause the disease.

Contaminated vomiting and feces

Especially when the patient has a viral version of the disease – which is the most common situation, especially for children – the virus can be transmitted through the patient’s vomit and feces.

Contaminated food

A frequent means of transmission is food contamination.

The use of water containing bacteria, parasites or viruses to cook or wash food can cause foods washed with it to transmit the disease.

There is also the possibility that the food has the microorganisms in it since planting and hygiene procedures are not taken.

It is also possible that someone infected with a virus that causes gastroenteritis, when cooking, contaminates food. This is especially common if there is no proper hand hygiene.

Food poisoning

Some bacteria, such as E. coli and Salmonella , cause food poisoning, and in these cases, this can lead to gastroenteritis. It is important that the source of the food is properly known to ensure that food poisoning will not happen.

Risk factors

Although everyone can get gastroenteritis, some factors can increase a person’s chances of getting the disease. Are they:


Children have a weak immune system when compared to that of an adult because they have not yet been exposed to so many pathogens, which means they have not developed resistance yet.

Therefore, children are the majority of gastroenteritis patients.

The biggest cause of the disease is rotavirus. At the same time, most adults are immune to the most common varieties of rotavirus precisely because they were exposed in the first years of life.

This means that a child is much more likely to develop the disease when exposed to the virus than an adult.

Usually, older people are more affected by bacteria, which are not transmitted as easily.

Regions without basic sanitation

The lack of basic sanitation facilitates the contamination of water and food by parasites and bacteria that can cause gastroenteritis, since water used for both food irrigation and washing is not necessarily decontaminated.

Lack of hygiene

People who do not wash their hands or food are much more susceptible to contamination by agents that cause gastroenteritis. They can also transmit the disease to other people more easily.

Read more: Lack of hygiene and sanitation affect 1 in 4 health centers

Symptoms of gastroenteritis

The symptoms of gastroenteritis are directly caused by inflammation of the intestine and stomach. It is possible that the disease is asymptomatic, that is, without symptoms, especially when it affects adults.

When present, the manifestations usually appear from 12 to 72 hours after the contamination and can be the following:

Abdominal cramps

Abdominal cramps and abdominal pain, especially when very severe, are often associated with a bacterial cause of the disease.


Vomiting is one of the main symptoms of gastroenteritis. Inflammation of the stomach and intestine can cause the patient to experience cravings that culminate in severe vomiting. In rare cases, this is the only symptom presented.


Diarrhea, along with vomiting, is one of the main symptoms related to gastroenteritis.

The regions of the intestine that are inflamed cannot fulfill their function and the fecal cake passes directly through them, taking too much liquid that escapes in the form of diarrhea, which usually lasts around 5 to 7 days.

Usually, the symptom is accompanied by vomiting and it is rare that a gastroenteritis presents with only one of them.

In cases where the disease is caused by the E. coli bacteria , it is common for blood to be mixed with the feces.


fever is the body’s reaction related to the inflammatory process. This symptom is usually present only in cases where the infection is viral.

Fever can cause problems, such as seizures and dehydration, if ignored.

Headache and muscle

Like fever, headache and muscle pain are usually related to viral causes.

How is the diagnosis made?

The diagnosis of gastroenteritis is made through clinical evaluation and stool examinations, in addition to the differential diagnosis, which is the elimination of other conditions with similar symptoms.

Appendicitis, cholecystitis and ulcerative colitis should be excluded before confirmation of gastroenteritis.

The doctor who diagnoses a gastroenteritis is the general practitioner and the gastroenterologist .

Clinical evaluation

In the clinical evaluation, the doctor talks to the patient about the symptoms. In some cases, it is possible that the list of symptoms is long enough for the doctor to diagnose gastroenteritis.

However, as the treatment of the disease may vary depending on the cause, further tests may be necessary to discover it.

Digital rectal examination may be necessary , which may reveal blood and intestinal wounds.

Stool examination

The stool test is done to confirm the type of infection that is causing gastroenteritis.

In the fecal sample, rapid tests can be performed for viruses, such as rotavirus or adenovirus, as well as bacterial culture, which allows observation and evaluation under the microscope.

In the fecal sample it is also possible to perform an immunological examination, which can reveal the eggs of parasites that may be causing the disease.

Read more: Stool examination can be effective in preventing colorectal cancer

Is gastroenteritis curable?

Yes. It is common for the patient to cure the disease alone. Especially in viral cases, the immune system – even that of children – tends to adapt and beat the virus quickly.

In some cases, such as those involving parasites or bacteria, certain specific medications can be used to fight infection.

What is the treatment of gastroenteritis?

In most cases, so-called supportive treatment is sufficient. It aims to protect the body from complications until the immune system clears the infection.

In the case of gastroenteritis, ensuring that the patient is well hydrated can be enough for him to recover in a few days.

In specific cases, medications can be used, which can be antibiotics , antiparasitic , antidiarrheal drugs , among others.

The disease usually has a cycle of approximately two weeks, varying slightly according to the type of infection.


Antibiotics are drugs focused on eliminating bacteria. They are not usually indicated for the treatment of gastroenteritis since, in most cases, the immune system can deal with the disease and there are side effects.

For example, patients infected with E. coli , when treated with antibiotics, can develop hemolytic-uremic syndrome, a serious disease that causes kidney failure.

The E. coli is a major cause of gastroenteritis therefore without confirmation by examination of stool that this is an infection by a bacterium that requires this type of treatment, such as a Campylobacter or Shigella , antibiotics do not are recommended.

Read more: Misuse of antibiotics creates superbugs that can kill


Antiparasitic drugs are aimed at eliminating parasites. It is the treatment used for cases such as giardiasis , an infection caused by the parasite Giárdia.

They can also be used to treat other parasitic infections that can cause gastroenteritis.


Antidiarrheal drugs are used to reduce diarrhea caused by the disease. It is important to remember that antidiarrheals are a possible cause of worsening of gastroenteritis when it is caused by the bacteria E. coli .

Therefore, they should not be used when there is blood mixed with the feces or even before the diagnostic confirmation of the causative agent.

Treatment for chronic diseases

In the case of non-infectious causes, such as the chronic diseases that cause gastroenteritis (Crohn’s disease, for example), treatment is usually focused on the cause.

Avoiding disease triggers – like avoiding milk if a person is lactose intolerant – is the most effective way to treat and prevent non-infectious gastroenteritis.

Medications for gastroenteritis

There is usually no need for drug intervention to treat gastroenteritis. However, when necessary, these are the medications used:


Antibiotics are drugs indicated for the elimination of bacteria. In cases of gastroenteritis, they are rarely recommended, but there are situations in which the doctor may prescribe them.

The main antibiotics used are:

  • Ciprofloxacin Hydrochloride ( Cyprus );
  • Doxycycline Hydrochloride ( Chlordox );
  • Metronidazole ( Flagyl );
  • Vancomycin Hydrochloride ( Vancocin );
  • Azithromycin ( Azimed );


Antiparasitic drugs are drugs used to eliminate parasites from the body.

Some of those that can be indicated to treat parasitic infections that cause gastroenteritis are:

  • Metronidazole ( Flagyl );
  • Tinidazol (Pletil);
  • Nitazoxanida ( Annita );


Antidiarrheals are medications indicated to reduce diarrhea in the patient. They are not indicated when the condition is caused by E. coli , but in some other cases they can be used to reduce the symptom.

Among them is Saccharomyces Boulardii ( Repoflor ).


These drugs are used to reduce symptoms, both of the infectious versions of gastroenteritis, and of inflammatory conditions that may be causing the disease. Are they:

  • Pednisolone ( Predsim );
  • Budesonida (Busonid).


NEVER self-medicate or stop using a medication without first consulting a doctor. Only he will be able to tell which medication, dosage and duration of treatment is the most suitable for his specific case. The information contained in this website is only intended to inform, not in any way intended to replace the guidance of a specialist or serve as a recommendation for any type of treatment. Always follow the instructions on the package insert and, if symptoms persist, seek medical or pharmaceutical advice.

Living together

Gastroenteritis is a disease that can be dangerous, so some precautions are important to ensure that the patient is well while recovering. Are they:


Rest is essential for patients with gastroenteritis to recover in health. Especially when it affects young children, the condition can make them tired and rest can help keep the immune system strong enough to beat the infection.


One of the most important precautions when dealing with gastroenteritis is hydration, especially when talking about children.

Diarrhea and vomiting can cause dehydration, which when severe can cause the patient’s death.

The patient should drink plenty of water and, if necessary, homemade serum . In the case of babies who still do not eat solids, it is recommended that the mother drink a lot of water and do not neglect breastfeeding.

Read more: Homemade serum: what it is for, measures and how to do it

Medical care

The diagnosis made by the doctor can indicate whether the condition needs drug treatment or not. It is important that the gastroenteritis patient consults to treat the disease and receive the necessary and appropriate instructions.

What should you eat when you have gastroenteritis?

The diet does not need to be changed because of gastroenteritis. Food is important to maintain the body’s energy and, therefore, periods over 4 hours without food intake are not recommended, and can weaken the body.

You should also not make changes to special diets, such as removing lactose if you do not have an intolerance.

However, in cases where there is an intolerance to some food, if it is present in the diet, it is recommended to remove it.

If you have lactose intolerance but take milk derivatives, this could be a possible cause of gastroenteritis. The same applies to celiac disease and other sensitivities.

Read more: Food in childhood: what to know


Despite being a disease that causes a large number of deaths annually, its prognosis is usually positive and in the vast majority of cases, the patient recovers well after a few weeks.

It is important that the treatment is followed properly, that the patient rests and hydrates well to avoid any complications.

Complications of gastroenteritis

Although gastroenteritis is a disease with a positive prognosis most of the time, there are some possible complications that should be noted. Are they:


Dehydration is the most common complication of gastroenteritis and is usually what causes the patient’s death when there is not adequate care. It is important for the person with the disease to hydrate as the water loss is high through vomiting and diarrhea.

Guillain-Barré syndrome

Guillain-Barré syndrome is an immune disease that causes great muscle weakness, which in some cases can affect respiratory muscles and cause risks to the patient’s life.

Approximately 0.1% of cases of gastroenteritis caused by Campylobacter bacteria develop the disease.

Reactive arthritis

Just as Campylobacter bacteria can cause Guillain-Barré syndrome, they can also lead to reactive arthritis , an inflammation of the joints caused by the immune system.

Approximately 1% of patients affected by gastroenteritis caused by this bacteria develop reactive arthritis.

Crohn’s disease

Crohn’s disease is an inflammatory condition of the digestive system. It can be both a cause of gastroenteritis and a consequence, as in some cases it can develop from intestinal infections.

It is a chronic disease that has no cure and requires prolonged treatment.

How to prevent gastroenteritis?

Prevention of gastroenteritis is possible. Although there are a large number of agents capable of causing the disease, the most common ones can be avoided. The main methods of prevention are:


There is a vaccine against rotavirus, the biggest cause of gastroenteritis. Vaccinating children prevents contamination by this virus, allowing the immune system to learn to deal with the contaminant without having to deal with the disease.


Hygiene is one of the most important steps to prevent this disease. Washing your hands thoroughly is essential, especially, but not only, after using the bathroom.

Proper food hygiene is also recommended.

If your region does not have treated water, you can boil it before using it to wash food, which eliminates microorganisms.

If you are sick, avoid cooking, as this can transmit the disease to other people.

Food storage

Keeping food in the proper environment is also important to prevent it from starting to rot and insects from getting close. Refrigeration is essential and no raw food should be left out of the refrigerator for more than 2 hours.


Basic sanitation is a way of preventing gastroenteritis because it prevents many agents that cause the disease from contacting the community in the region. This method of prevention is the responsibility of the authorities.


Children under 2 years of age must be fed with breast milk. This is relevant for the prevention of gastroenteritis as breastfeeding is a way to strengthen the child’s immune system.

This can guarantee some level of protection against the disease.

Canine gastroenteritis

It is not just humans who can suffer from intestinal inflammation. Our pets too. Dogs often experience this.

As in humans, gastroenteritis in dogs can cause vomiting and diarrhea. It is important to keep the animal’s water and food pots very clean, to prevent bacteria from reproducing in them and causing damage to the animal’s health.

Usually, the disease heals itself in approximately 2 days. In the meantime, it is important to hydrate the dog well and not feed it for approximately 24 hours.

Remember to remove only the food . The water lost during gastroenteritis needs to be replaced.

You must take your dog to the vet in some situations. If he is a puppy, if there is blood in the stool or vomit or if the condition lasts more than 2 days, especially if the animal is not eating after that time.

Canine hemorrhagic gastroenteritis

When a dog with gastroenteritis has blood in his stool or vomit, it is possible that he is dealing with a hemorrhagic version of the disease.

It is important to take him to the vet, as this can cause serious risks to the dog’s life.

Common questions

How long does gastroenteritis last?

The duration of the disease varies, depending on the cause. In general, viral gastroenteritis lasts from 7 to 10 days.

Typically, the peak of symptoms occurs for approximately 2 to 4 days, in any of the variants, but it can be more extensive if the treatment situation is precarious.

Is gastroenteritis contagious?

-Yeah . Gastroenteritis can be transmitted through vomiting and feces. A common way of transmission is through food. A patient who has not washed his hands properly can cook, contaminating all food, for example.

Hygiene is essential to prevent gastroenteritis from spreading.

What is traveler’s diarrhea?

Traveler’s diarrhea is gastroenteritis, but it gets its name because it affects people who are traveling. It is no different from common gastroenteritis.

It usually happens when a traveler ingests contaminated water or food in an unknown region and, because of that, the disease sets in, causing diarrhea.

There is no difference between traveller’s diarrhea and common gastroenteritis.

Gastroenteritis is a common disease, but it can be dangerous if ignored. Remember to hydrate yourself and take care of food hygiene and your daily life.

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