Stomach Bug: Causes, Symptoms, Treatments.

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A stomach bug often refers to viral gastroenteritis (also called stomach flu). Viruses are the most common cause of acute diarrheal illness in children and adults.

However, a stomach bug may also mean other types of infection of the gastrointestinal system, such as:

  • Bacteria.
  • Protozoa.
  • Parasites.

Stomach flu is one of the most widespread diseases worldwide. Today, you will learn all the basic facts about stomach viruses, including common viruses, symptoms, and treatments.


Table of Contents

1. How Common are Stomach Bugs (viruses)?

A stomach bug is often used to describe (viral gastroenteritis). It is typically a self-limiting disease, but it can lead to serious complications in infants and the elderly if left untreated.

2. Causes.

Main stomach viruses:

  1. Norovirus: The most common cause of stomach flu. Previously, it was the second most common before the widespread immunization against rotavirus. It often peaks during the winter months, affecting about 19-21 million cases of diarrhea each year in the USA.
  2. Rotavirus: it is less widespread nowadays due to widespread vaccine use. However, it is still a major cause in some underdeveloped countries.
  3. Astrovirus.
  4. Adenovirus.

Non-viral stomach bugs of diarrhea include bacteria such as staphylococcus aureus, shigella, salmonella, etc. Also, parasites such as Giardia and Cryptosporidium can cause acute diarrhea similar to viral gastroenteritis.

How do you get an infection:

You will get an infection through the mouth by:

  • Contacting an infected person.
  • Using the personal utensils of an infected person.
  • Contacting with an infected surface such as door handles, kitchen appliances, etc.
  • Eating contained food.
  • Contaminated water or drinks.

The stomach bug symptoms take an average of 24-48 hours to appear after the initial infection.

The norovirus is extremely stable in the environment and may cause outbreaks in a wide range of settings, such as:

  • Restaurants and catered events
  • Hospitals and long-term care facilities
  • Schools, childcare settings, and community centers
  • Municipal water contamination and recreational water exposure
  • Cruise ships and resorts
  • Military populations
  • Athletic teams
  • Rafters and backpackers
  • Natural disasters
  • Prisons

Common foods that transmit stomach viruses:

  • Green vegetables.
  • Fruits.
  • Mollusks.
  • Salads.
  • Shellfish.
  • Sandwiches.
  • Frosting.
  • Celery.
  • Melons.
  • Raspberries.

Is stomach bug contagious?

Stomach bugs such as stomach viruses are highly contagious. They may spread from person to person directly or through contaminated utensils and food.

A person with stomach virus symptoms may remain contagious for a few days after recovery. And the virus can remain in the stool for up to two weeks. Learn More.


  • Acute onset diarrhea: three or more bowel motions of diarrhea or loose stool per day.
  • Nausea (in 93% of patients).
  • Vomiting (81%).
  • Abdominal pain (in 76% of the patients).
  • Cramps are typically in the lower abdomen (colics that come and go).
  • Low-grade fever.
  • Malaise and fatigue.
  • Muscle aches.
  • Respiratory symptoms such as sore throat, cough, and runny nose are present in about 10% of the cases.
  • Weight loss in prolonged cases.

Stomach bug complications (Alarming symptoms):

Stomach bugs may cause significant dehydration with subsequent shock and determination of the consciousness in age extremes (infants and the elderly).

So, it is important to watch for any alarm symptoms in infants and older adults with stomach flu:

  • Extreme thirst.
  • Dryness of saliva (dry mouth).
  • Dryness of eyes (scanty tears).
  • Shortness of breath.
  • Peeing too little urine.
  • Dark (deep yellow) urine.
  • Dizziness, lightheadedness.
  • Fainting attacks.
  • Confusion.
  • Coma.
  • Week pulse.
  • Cold, clammy extremities.
  • Low blood pressure.

Go to the ER immediately if a stomach bug infection is associated with one or more of the above red-flag signs and symptoms.

How long does a stomach bug last?

The stomach bug symptoms (stomach flu) typically last for a few days. However, the symptoms may last up to two weeks. For instance, norovirus diarrhea lasts for two days on average, while rotavirus diarrhea lasts for three to eight days.

Mimics of Stomach bug symptoms:

Stomach bug (viral gastroenteritis) symptoms (diarrhea, vomiting, nausea, and abdominal pain) may mimic other acute conditions such as:

  • Bacterial gastroenteritis (as with salmonella, shigella, etc.).
  • Parasitic infections such as Giardiasis and cryptosporidium
  • an attack of food intolerance or food allergy.
  • Drug-induced diarrhea (such as antibiotic-associated diarrhea).


No medications can kill stomach viruses. Instead, they are self-limiting infections. As a result, the vomiting and diarrhea often resolve spontaneously within a couple of days.

We aim by treatments to prevent and treat its complications. For example:

  • Eating bland, easy-to-digest food such as the BRAT diet (Bananas, Rice, Apple sauce, and Toast).
  • Avoid foods that may aggravate vomiting and diarrhea, such as fatty foods, spicy foods, caffeine, alcohol, and fast foods.
  • Staying hydrated is the most crucial step in preventing complications of stomach flu (frequently drink small amounts of water.
  • Over-the-counter anti-nausea and anti-vomiting medications such as Pepto-Bismol.
  • Over-the-counter antispasmodic for abdominal pain.
  • A probiotic may also help
  • Zinc supplementation
  • ORS (oral rehydration solutions) may be needed for young infants.

When to go to the hospital?

Go to the hospital if the stomach bug infection is associated with the following:

  • Sings of volume depletion/dehydration (dry mouth, extreme thirst, cold extremities, etc.).
  • Refractory vomiting
  • Confusion or peeing too little urine.
  • Excessive bloody stool or anorectal bleeding
  • Severe abdominal pain
  • Prolonged symptoms (more than one week in adults)
  • Age 65 or older with signs of hypovolemia
  • Comorbidities (e.g., diabetes mellitus, immunocompromised)
  • Pregnancy.