Is the Stomach Flu Contagious?

Stomach flu (viral gastroenteritis) is caused by a number of different viruses. It is contagious, spreading from person to person through contact with an infected person’s stool or vomit.

Stomach flu, also called viral gastroenteritis, occurs when a person's stomach and intestines become infected with a virus that can cause diarrhea and vomiting. 

What Are Symptoms of Stomach Flu?

The hallmark symptoms of stomach flu (viral gastroenteritis) usually start suddenly, can be severe, and include: 

• Diarrhea (may be watery)
• Vomiting
• Both

Diarrhea and vomiting can lead to loss of fluids (dehydration). Symptoms of dehydration include: 

• Thirst
• Dry mouth
• Tiredness 
• Dizziness
• Confusion 
• Dark yellow urine
• Urinating less than usual, or no wet diapers for 3 hours or more in babies
• Lightheadedness or fainting
• Poor skin turgor (how quickly the skin returns to normal after being pinched)
• Sunken eyes or cheeks
• Urinating less than usual
• No tears when crying (in children)

See a doctor right away if you experience symptoms of dehydration. Severe dehydration can be life-threatening. 

Other symptoms of stomach flu include: 

• Fever
• Headache 
• Muscle aches
• Abdominal pain or cramping
• Loss of appetite

Stomach flu (viral gastroenteritis) is caused by a number of different viruses. However, despite it being called “stomach flu,” influenza (flu) viruses do not cause viral gastroenteritis. 

Common viral causes of stomach flu include:

• Norovirus
  • The most common cause of viral gastroenteritis
  • Symptoms usually begin 12 to 48 hours contact with the virus and last 1 to 3 days
• Rotavirus
  • Symptoms usually begin about 2 days after contact with the virus and last for 3 to 8 days
  • Vaccines can prevent rotavirus infection
• Adenovirus
  • Symptoms typically begin 3 to 10 days after contact with the virus and last 1 to 2 weeks
• Astrovirus
  • Symptoms typically begin 4 to 5 days after contact with the virus and last 1 to 4 days.

In the U.S., norovirus, rotavirus, and astrovirus are more likely to cause stomach flu in the winter.

Stomach flu (viral gastroenteritis) is caused by viruses and is contagious. It spreads from person to person through contact with an infected person’s stool or vomit. 

Norovirus is particularly contagious, and often spreads in places where a lot of people congregate, such as households, schools and day care centers, nursing homes, cruise ships, and restaurants.

Infection can occur when someone:

• Touches an infected person or a contaminated surface and doesn’t wash their hands
• Consumes foods or drinks with the virus in them

Stomach flu (viral gastroenteritis) is usually diagnosed with a physical examination and a patient’s history. Tests to determine the specific virus that is causing the illness may include: 

• Blood tests
• Urine tests
• Stool tests

Most of the time symptoms of stomach flu (viral gastroenteritis) go away on their own and treatment is not needed. 

Treatment is aimed at relief of symptoms and preventing dehydration. 

• Drink plenty of fluids
• Older children and adults can drink sports drinks
• Babies and young children may be given an oral rehydration solution, such as Pedialyte
• Breastfeeding babies can continue to breastfeed
• Avoid drinks with a lot of sugar, like juice or soda that can worsen diarrhea 
• Severe dehydration may need to be treated in a hospital 
• Intravenous (IV) fluids may be given

For patients able to keep food down: 

• Eat lean meats, fruits, vegetables, and whole-grain breads, and cereals
• Avoid foods with a lot of fat or sugar, which worsen symptoms

Loperamide (Imodium) may be taken for 1 to 2 days to stop diarrhea if you: 

• Are an adult younger than 65 years 
• Have a new bout of diarrhea
• Have no fever and no blood in bowel movements
• Patients older than 65, have a fever, or have blood in your bowel movements, should not take loperamide without first checking with a doctor
• Do not give anti-diarrheal medicines to children

Antibiotics are not used to treat stomach flu, which is caused by viruses, because antibiotics only treat bacterial infections.

The best ways to help decrease the risk of getting stomach flu (viral gastroenteritis) include: 

• Avoiding contact with anyone who has stomach flu
• Washing your hands with soap and water for at least 20 seconds after using the bathroom, before you eating, or after changing a diaper
• Having your baby receive the rotavirus vaccine
  • Rotavirus commonly causes viral gastroenteritis in children