Stomach flu typically spreads when people have contact with infected stool, vomit, objects, or surfaces and do not wash their hands properly. This can lead to them ingesting the virus through the mouth.

People may transmit stomach flu to others after their symptoms resolve.

Stomach flu and stomach bug are alternative names for viral gastroenteritis, a condition affecting the intestines.

The Centers for Disease Control and Prevention (CDC) estimates that acute gastroenteritis is responsible for around 179 million illnesses in the United States each year.

Despite the name, stomach flu is actually an infection of the intestines. Influenza viruses do not cause it. In fact, several other viruses cause stomach flu, including:

  • norovirus
  • adenovirus
  • rotavirus
  • astrovirus

This article explores how stomach flu spreads and how long the condition is transmissible. It also discusses stomach flu symptoms, treatments, prevention, and when to speak with a healthcare professional.

Two people's hands holding onto a rail with a superimposed red mark 1Share on Pinterest
Sol de Zuasnabar Brebbia/Getty Images

Stomach flu spreads from one person to another through contact with the vomit or stool of a person with the infection.

If someone contracts stomach flu, their vomit and stool will contain the virus. The virus can infect other people at this stage. This can happen if tiny bits of stool or vomit are present on a surface, someone touches that surface, and they then touch their mouth, nose, or eyes without washing their hands first.

People may also transmit viral gastroenteritis if they do not wash their hands thoroughly before:

  • touching surfaces or objects that other people might use
  • preparing food for people
  • interpersonal physical contact, such as shaking hands, hugging, or administering medical care

Norovirus is highly contagious. The virus can survive for months on surfaces. When a person with a norovirus infection vomits, airborne particles of the virus can land on surfaces or infect other people if they breathe them in.

If water comes into contact with the stool of people with stomach flu, the water may become contaminated. The contaminated water can transmit the virus to foods or drinks.

People who consume these foods or drinks may contract stomach flu. People who swim in contaminated water may also contract the infection.

People with stomach flu who do not have any symptoms can still transmit the infection.

According to the CDC, if a person has a norovirus infection, they can still transmit it for up to 2 weeks after they feel better since the virus remains in their stool.

People can potentially transmit stomach flu in any place where people congregate in close quarters, such as:

  • shared households
  • schools
  • universities
  • day care centers
  • bars and nightclubs
  • offices
  • nursing homes
  • sports stadiums
  • restaurants
  • cruise ships

Learn more about how long stomach flu is contagious and how long it lasts.

Symptoms of stomach flu include:

The most common complication of stomach flu is dehydration. Drinking plenty of liquids can help prevent this complication.

Most people who contract stomach flu recover on their own with plenty of rest and fluids. Treatment primarily focuses on replacing fluids.

Doctors may recommend drinking oral rehydration solutions alongside water to help replace the electrolytes a person may have lost through vomiting and diarrhea or sweat if they had a high fever.

If someone cannot hold down food and drink and continues to vomit, they may try slowly sipping small amounts of water or other clear fluids or sucking on ice cubes.

Liquids that can help replace electrolytes include:

A person can take the following steps to help prevent contracting viral gastroenteritis:

  • Vaccinate infants against rotavirus, which is a common cause of viral gastroenteritis.
  • If a person has any symptoms of stomach flu, they should not touch or prepare food for someone else.
  • Wash hands thoroughly, especially after working with food, using the restroom, or changing a diaper.
  • Wipe down surfaces with a disinfectant spray, particularly if stool or vomit has touched the surface, such as on a diaper changing surface.
  • Wash any garments or textiles, especially if they may have touched the stool or vomit of someone with stomach flu.

If someone suspects they may have viral gastroenteritis, it is crucial they talk with a doctor. A doctor can make sure the person has stomach flu and not another condition, such as food poisoning or bacterial gastroenteritis.

Gastroenteritis caused by other pathogens, like bacteria, can replicate the symptoms of viral gastroenteritis. However, these conditions require different treatments. They may have higher life threatening risks of complications as well.

People can contract and transmit viral gastroenteritis, or stomach flu, through contact with the vomit or stool of someone with the infection. Individuals with stomach flu may also transmit airborne germs when they vomit.

Treatment for stomach flu centers on rehydration and replacement of electrolytes. A person should speak with a healthcare professional if they have any symptoms of stomach flu.