Is the Stomach Flu (Gastroenteritis) Contagious?

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

What is the stomach flu?

Stomach flu or gastroenteritis is a general term for a number of inflammatory problems that occur in the gastrointestinal tract. Gastroenteritis is a better term because when some individuals use the term "stomach flu," they get the term confused with the flu (influenza) and the viruses that cause the flu. Influenza viruses do not cause stomach flu.

Gastroenteritis most commonly causes symptoms of:

Other symptoms may include the following:

Because stomach flu means gastroenteritis and, because when the term “stomach flu” is used, the readers usually mean acute gastroenteritis caused by viruses (mainly Norovirus), the emphasis of this article will be on Norovirus- caused gastroenteritis although other causes will be mentioned.

Is the stomach flu contagious?

Unfortunately, there are many causes of stomach flu. The most common causes are contagious gastroenteritis are

However, there are many other causes of gastroenteritis that are not contagious such as:

Many medications list gastroenteritis is a common side effect.

Quick GuideDigestive Disorders: Common Misconceptions

Digestive Disorders: Common Misconceptions

Abdominal Pain Symptoms

Abdominal pain is one symptom of the stomach flu, however, there are a variety of causes of abdominal pain such that includes

  • indigestion after eating,
  • gallstones and gallbladder inflammation,
  • pregnancy,
  • gas,
  • IBD (ulcerative colitis and Crohn's disease),
  • ulcers, and
  • gastritis.

How will I know if I have the stomach flu (signs and symptoms)?

The primary symptom of stomach flu or gastroenteritis is diarrhea that does not contain blood usually accompanied by nausea, some occasional vomiting, and abdominal cramping.

The incubation time for gastroenteritis varies according to the particular cause. The most rapid incubation time is usually with viral illnesses (for example, for Norovirus, which is about 1 -2 days), and the infected person may become contagious during this time without symptoms of nausea or diarrhea.

Noncontagious causes (allergies, toxins, medication side effects) may produce symptoms very rapidly (minutes to hours) and in some people, the symptoms may become so severe that they require emergency care.

Doctors usually base the diagnosis on the person's history and physical exam; some patients will need further blood and fecal tests done to determine the cause, especially in more severe infections.

How is stomach flu spread?

  • Contagious causes of stomach flu (gastroenteritis) are spread usually through contamination of food or water or by person-to-person (fecal – oral route) spread via contaminated droplets containing infectious organisms.
  • Some of the contagious causes of gastroenteritis (most notably, Norovirus) can be spread by kissing and other close personal contact or on surfaces where droplets containing viruses or other agents survive.
  • Some viruses can even be spread to household pets such as dogs that, in turn, can spread the disease to other people.
  • Fortunately, most causes of contagious gastroenteritis are not spread by breastfeeding or through breast milk.
  • Noncontagious gastroenteritis such as that related to side effects of medicine or food allergies is not spread from person to person.

How long does the stomach flu last?

For contagious causes of stomach flu, many individuals have symptoms that last about 2 to 5 days, after which the symptoms tend to resolve. Once the symptoms resolve, an individual may be considered "cured" of stomach flu. However, it's not unusual for that same individual to develop stomach flu again at some point in time if they are exposed to other causes, or in some individuals, the same infectious cause. Occasionally, the stomach flu "symptoms" progress and goes on to become another more severe disease (for example, salmonellosis or shigellosis).

When is stomach flu contagious (how long is it contagious)?

Stomach flu is contagious when the organisms that cause stomach flu are spread to uninfected individuals. The timeframe or how long the infected person remains contagious depends on the infecting cause. For example, most common cause of stomach flu is Norovirus. It has an incubation period of about 12 - 48 hours, and can cause the person to be contagious during the incubation period and for as long as they shed virus (usually about three days after symptoms stop but sometimes up to two weeks). Norovirus symptoms usually last about one to two days and is sometimes termed the 24 hour stomach flu.

Other infectious agents such as other viral strains, bacteria, and other infectious agents have incubation periods and contagious periods unique to them. Because this is an introductory article about stomach flu, readers are recommended to check the incubation periods and contagious periods of whatever infectious agent is thought to be causing the problem (for example, Salmonella or E. coli).

How long is stomach flu contagious on surfaces?

The most common cause of stomach flu, noroviruses, can live on surfaces for up to about two weeks. Consequently, is important to try to avoid contaminating surfaces while you are infected with the virus and equally important, anyone not infected individual should wash their hands with soap and water after touching surfaces that might be contaminated. Cleaning surfaces like doorknobs or kitchen counters with a diluted bleach and water solution can help reduce the chance of infection.

For other causes of stomach flu (gastroenteritis), the reader is suggested to look up the specific infectious agent to determine how long it will remain viable and contagious on surfaces.

When should I contact a health-care professional about the stomach flu?

Many people get contagious stomach flu from different causes, but in general, they recover from the infection in about 2 to 5 days and usually do not contact a health-care professional. Most doctors consider gastroenteritis to be a self-limiting disease. Unfortunately some people, especially the elderly, young children, and individuals that have multiple medical problems may develop more severe symptoms. Consequently, people should contact their health-care professional or emergency department if one or more the following occurs:

  • Gastroenteritis symptoms that last more than five days
  • The intensity of the symptoms increases
  • A fever above 101 F or 38.3 C
  • Bloody diarrhea
  • Signs of dehydration appear, for example, little or no urine output or dry mucous membranes
  • Constant or increasing abdominal pains
  • A person is immunocompromised, has other medical problems, or is pregnant
  • Facial or throat swelling
  • Shortness of breath

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Medically Reviewed on 10/11/2017

Centers for Disease Control and Prevention. Norovirus. Aug 13, 2016

Diskin, A., MD. "Emergent Treatment of Gastroenteritis." Medscape. Feb 10, 2017.

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