What is stomach flu (gastroenteritis)?

Gastroenteritis is inflammation (irritation) of your intestines. People usually call it a “stomach bug” or “stomach flu,” even though it’s not limited to just influenza. Although most people report stomach pain, gastroenteritis can also involve your small intestines and colon.

How common is stomach flu (gastroenteritis)?

Stomach flu is common. More than 20 million people get sick each year in the U.S. with an intestinal upset. Viruses are the most common cause of stomach flu.

Who gets stomach flu (gastroenteritis)?

Anyone can come down with stomach flu. But you’re more likely to get it if you’re in a place where lots of people share living or dining spaces, such as:

  • Children in daycare or at camp.
  • Nursing homes.
  • Students living in dormitories.
  • Military personnel.
  • Prisons.
  • Psychiatric wards.
  • Cruise-ship passengers.
  • Travelers to less-developed countries.
  • Anyone with immune compromised state.

What causes stomach flu (gastroenteritis)?

You can get sick from bacteria, parasites, toxins and viruses. Viruses are the most common cause of so-called stomach flu. Norovirus is often the culprit for adults, while rotavirus is frequently to blame for stomach flu in children. These viruses mostly infect the lining of the small intestine.

What are the symptoms of stomach flu (gastroenteritis)?

The main symptom of gastroenteritis is diarrhea. When the GI tract becomes infected during gastroenteritis, multiple activities from the virus brings on diarrhea. Malabsorption occurs because of the destruction of the gut cells called enterocytes. The virus can also disrupt the reasbsorption of water and induce secretory diarrhea, which is responsible for the loose liquidy stools.

Can stomach flu cause a fever?

You might get a fever when you have stomach flu. A fever can be a sign that your body is fighting an infection. You may feel sweaty, clammy or have the chills. You may also get a headache or ache all over your body.

Is the stomach flu worse in some people?

In general, most people recover quickly from the stomach flu. Symptoms can be worse in babies, young children, older adults or anyone of any age that is immune-compromised. Vomiting and diarrhea can cause dehydration (not enough water in the body) within just a short period of time, depending on the circumstances. Signs of dehydration include:

  • Extreme thirst.
  • Less urine output than usual (no wet diapers for three hours or more in infants).
  • Urine that is darker in color.
  • Sunken cheeks or eyes.
  • Lightheadedness, dizziness upon standing.
  • General weakness.

Why does stomach flu hit at night?

In some people, the stomach flu symptoms may be more pronounced at night due to their circadian rhythm. At night an increase in immune system activity releases infection-fighting chemicals. These can cause inflammation that make you feel worse as you battle your flu.

Is stomach flu (gastroenteritis) contagious?

Viral stomach flu spreads easily to others. You can catch a stomach flu virus any time of the year, but the common norovirus is more widespread from November to April when people tend to be more indoors. Because a variety of viruses can cause stomach flu, you might get different versions of gastroenteritis many times throughout life.

It’s spread from person to person by coming into contact with tiny, invisible particles from a sick person’s stool or vomit if you:

  • Touch a surface and come in contact with the germs and you touch food or your mouth.
  • Eat or drink food or beverages that have a sick person’s germs.
  • Have close contact with someone who has stomach flu (even if they have no symptoms).

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