Gastroenteritis refers to inflammation in the intestines and stomach. Viral gastroenteritis can cause symptoms such as diarrhea and vomiting. Stool tests may help with gastroenteritis diagnosis.

In the United States, norovirus is the most common cause of diarrhea and vomiting as a result of acute gastroenteritis. Annually, it affects 19–21 million people and causes around 900 deaths, predominantly in adults ages 65 years and over.

Most of the time, viral gastroenteritis lasts less than 1 week and does not require medical intervention. However, stool tests can help confirm whether a person has an infection, signs of inflammation, or other digestive conditions.

This article discusses stool tests for infectious gastroenteritis in more detail. It also discusses gastroenteritis diagnosis, treatment, prevention, and when to speak with a healthcare professional.

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A person who contracts norovirus, which is one possible cause of viral gastroenteritis, may find their symptoms clear completely within about 1–3 days. Unless they become dehydrated, they will likely not need to contact a doctor.

If a person does contact a doctor about infectious gastroenteritis symptoms, the doctor may order a stool test. Infectious gastroenteritis refers to inflammation in the stomach and intestines that occurs due to the presence of a pathogen, such as bacteria or a virus.

Healthcare professionals can use a stool test to check for the presence of infections, which commonly include viruses such as norovirus and rotavirus. A healthcare professional may also check for signs of inflammation or the presence of other health conditions that affect the digestive system.

If a healthcare professional requests a stool test, a person will need to collect a sample of stool in a container that a doctor or lab provides. Once a person collects the sample, they should follow any instructions about where to send or take the container for analysis.

A 2019 study suggested that the guidelines for testing stool due to gastroenteritis in children may need updating to increase the frequency that healthcare professionals test stool. The researchers suggest that this could help them identify cases of bacterial gastroenteritis that may pose a greater health threat to the general population.

Most people will not experience symptoms of gastroenteritis for a long period of time and will not need to seek medical treatment or diagnosis.

If a person does seek medical evaluation, a doctor will likely perform a physical exam, discuss a person’s medical history, and may order a stool sample.

During the physical exam, a healthcare professional will check a person’s blood pressure and heart rate and for any signs of dehydration and fever. They may also use a stethoscope to listen to sounds in the abdomen and tap on the abdomen to check for tenderness or pain.

In some cases, they may perform a rectal exam, which involves a doctor sliding a gloved, lubricated finger into a person’s anus to check for blood in their stool.

A healthcare professional will also likely ask questions about a person’s medical history, which may include questions about the type, length, duration, and frequency of symptoms. They may also ask about any recent travel, recent exposure to people who are feeling unwell, and history of other health complications.

A healthcare professional may also order a stool sample to check for infection, inflammation, and other digestive health conditions.

Gastroenteritis does not typically require any specialized treatments. Viral infections will often resolve within a few days.

Treatment often focuses on keeping a person hydrated with fluid and electrolytes. This may include drinking plenty of fluids, such as:

Other possible treatments a doctor may recommend include:

However, if a person has another type of pathogen, such as bacteria or fungi, a healthcare professional may recommend different treatments to manage the infection.

A person can take steps to help prevent the transmission of pathogens that cause gastroenteritis, such as norovirus. They may include:

  • frequently hand washing with soap and water for at least 20 seconds, and in particular:
    • before taking or giving someone else medication
    • before eating, preparing, or handling food
    • after using the toilet or changing diapers
  • cooking shellfish completely to an internal temperature of at least 145°F (63°C)
  • rinsing off vegetables and fruits before eating or cooking
  • cleaning and disinfecting all surfaces and thoroughly washing all laundry that may have come into contact with vomit or stool
  • not preparing food for other people if a person has gastroenteritis or has experienced gastroenteritis symptoms within the past 2 days

A person may not need to contact a doctor for diarrhea and vomiting as a result of acute gastroenteritis. Symptoms of norovirus, which is the most common cause of viral gastroenteritis, typically clear within about 3 days.

If a person with stomach flu has another health condition, such as a weakened immune system, kidney disease, or inflammatory bowel disease, they should contact a doctor straight away. Pregnant people and older adults should also speak with a healthcare professional as soon as possible.

Additionally, if a person experiences the following symptoms, they should speak with a doctor immediately:

  • symptoms of dehydration
  • passing six or more loose stools in a day
  • high fever
  • changes in mental state, such as fatigue or confusion
  • diarrhea that lasts for longer than 2 days
  • severe abdominal or rectal pain
  • frequent vomiting
  • passing stools that contain blood or pus

Stool tests are a type of lab test for gastroenteritis that check for common causes of infection, inflammation, and other health conditions that affect the digestive system.

Treatment for viral gastroenteritis typically involves making sure a person gets enough fluids and electrolytes. Certain medications may help to ease some symptoms, such as diarrhea.

A person should speak with a doctor if their symptoms last for more than a few days, if they become dehydrated, or notice certain symptoms, such as blood in their stool.