Viral gastroenteritis (stomach bug)

Overview

Viral gastroenteritis is an infection of your intestines caused by a virus. People often call it the "stomach flu" or a "stomach bug," but it isn't caused by flu viruses, and the flu vaccine doesn't protect against it.

It comes on suddenly and usually goes away on its own within a few days. The biggest danger is dehydration: losing more fluid from vomiting and diarrhea than you take in. Babies, young children, older adults, and people with a weak immune system get dehydrated faster.

Symptoms

Symptoms usually start suddenly, 12 to 48 hours after you catch norovirus. Other viruses can take a few days.

• Watery diarrhea
• Nausea and vomiting
• Stomach pain or cramps, often around the belly button
• Sometimes a fever

Less common

• Headache
• Body aches and chills
• Feeling tired

How it usually goes

• Day 1: Vomiting and diarrhea often start suddenly. Sip fluids in small amounts. You're very contagious.
• Days 2–3: Vomiting usually stops first. Diarrhea gets better. Start eating normal foods as your appetite comes back.
• Days 4–7: Most people are better. Some viruses take longer. You can still spread it for up to 2 weeks, so keep washing your hands well.

Look up a symptom: Fever

When to get medical care

Causes

Many viruses can cause a stomach bug. Norovirus is the most common, and it infects people of all ages. Rotavirus, adenovirus, and astrovirus most often infect babies and young children. Bacteria, parasites, and some chemicals can cause similar illness, like food poisoning.

These viruses spread through tiny bits of an infected person's stool or vomit. You can catch one by touching a surface with the virus on it, eating food or drinking water made by someone who's sick, or shaking hands. Norovirus can float in the air when someone vomits, and it can live on countertops for months. People can spread it before they feel sick and for up to 2 weeks after.

Does it spread or run in families?

• Yes, it can spread from person to person.
• How it spreads: germs from poop getting into the mouth, touch, coughs, or sneezes.
• Washing hands often and staying home when sick help protect others.

Who is more likely to get it

• Babies and young children, who catch it often and get dehydrated quickly
• Older adults, who are more likely to get dehydrated
• People with a weak immune system, who may have worse or longer symptoms
• Close quarters, like daycare, schools, nursing homes, and cruise ships

Possible complications

• Dehydration: The most common problem; can be serious in babies and older adults
• Trouble digesting milk: Can last a month or more after the illness

Diagnosis

Most people don't need a visit or a test. If you see a healthcare professional, they'll usually know it's a stomach bug from your symptoms. They'll also check for dehydration and make sure it isn't something that needs other treatment.

Questions you may be asked

• When the vomiting and diarrhea started, and how many times a day
• Whether you can keep fluids down, and how often you're urinating
• Whether there's blood in your stool or vomit
• Whether others around you are sick, and what you ate recently
• Recent travel, antibiotics, or hospital stays

The exam

They'll check your temperature, blood pressure, and pulse, look for signs of dehydration like a dry mouth or sunken eyes, and press gently on your belly to check for tenderness.

Tests

Tests usually aren't needed for mild symptoms that go away quickly. Your healthcare professional may order a test if symptoms are severe or last a long time:

• Stool test: Checks for viruses, bacteria, or parasites, or for blood in the stool.
• Blood tests: If you're very dehydrated, to check your body's salt and mineral levels and kidneys.

Treatment

There's no medicine that cures a stomach bug, and antibiotics don't work on viruses. Treatment means replacing the fluids and salts your body loses, while the virus runs its course.

Self-care

• Sip fluids often, in small amounts if you're vomiting: water, broth, sports drinks, or diluted juice
• Use an oral rehydration solution (like Pedialyte) for children, older adults, and anyone with lots of diarrhea or signs of dehydration
• Babies should keep drinking breast milk or formula; ask a doctor before giving a baby a rehydration solution
• Eat your normal foods when your appetite comes back, even if you still have diarrhea. Fasting and strict diets don't help.
• Go easy for a few days on caffeine, fatty or fried foods, very sugary drinks, and milk, which can make diarrhea worse for some people
• Rest, and wash your hands well after using the bathroom

Medicines

Most people don't need medicine. Some over-the-counter medicines can ease diarrhea in adults. Read the label, and ask a pharmacist if you take other medicines.

Medicine names link to drug information from the U.S. National Library of Medicine (MedlinePlus). OwieClear doesn't give doses: follow the label or your healthcare professional.

If you're badly dehydrated or can't keep any fluids down, you may need fluids through an IV at a clinic or hospital. A doctor can also prescribe medicine to stop severe vomiting.

How it compares

Prevention

Good handwashing and cleaning are the best ways to stop a stomach bug from spreading. A rotavirus vaccine protects babies.

• Wash your hands well with soap and water after using the bathroom or changing diapers, and before making or eating food
• Clean surfaces after someone vomits or has diarrhea with a bleach mix (5 to 25 tablespoons of household bleach per gallon of water)
• Wear gloves to handle dirty laundry, wash it on the longest cycle, and machine dry it
• Don't make food for others while you're sick and for 2 days after you feel better
• Wash fruits and vegetables, and cook oysters and other shellfish well
• Babies should get the rotavirus vaccine by mouth, starting at 2 months

Which doctor treats this

• Start with your primary care provider (family doctor or internist).
• They may send you to a gastroenterologist (stomach and gut doctor).

Back to school, work, or sports

• Stay home until 2 days after vomiting and diarrhea stop, especially if you work with food, children, or patients.
• Wash hands well after using the toilet.

Children, pregnancy, and older adults

• Babies and children: Diarrhea can make a baby badly dehydrated in a day or two. Call a doctor for advice early. Keep feeding breast milk or formula. Watch wet diapers closely, and call if there's none for 3 hours or more.
• Pregnancy: See a healthcare professional right away if you're pregnant and have symptoms. Dehydration can be harder on your body during pregnancy.
• Older adults and people with a weak immune system: See a healthcare professional right away for any symptoms, since dehydration can happen faster and be more serious.

Pregnancy and breastfeeding

• If you're pregnant or planning to be, tell your prenatal provider about this condition.
• Some infections can pass to the baby during pregnancy or birth. Tell your provider if you've been exposed.
• Don't start or stop any medicine on your own. Some are safe in pregnancy and some need to be changed.
• Ask before taking any pain reliever. The FDA advises avoiding ibuprofen and naproxen after 20 weeks unless your doctor says to.
• Breastfeeding: Most medicines are fine, but ask. The NIH LactMed database lists what's known about each one.

Outlook

Most people get better in a few days without treatment. Your appetite may take a little longer to come back. Some people have trouble digesting milk for a few weeks afterward. Dehydration is the main danger, and it can be prevented by drinking enough fluids.

Myths and facts

Getting ready for your visit

If you need to see a healthcare professional, a little preparation helps you get the most from a short visit.

What to bring

• When symptoms started, and how many times a day you're vomiting or have diarrhea
• How much you're drinking and how often you're urinating (or wet diapers for a baby)
• Your highest temperature
• All medicines you take, and any recent antibiotics or travel

Questions to ask

• Am I (or is my child) dehydrated?
• Which drinks should we use, and how much?
• Is it safe to take an anti-diarrhea medicine?
• When can I go back to work, or my child back to school or daycare?

Research studies

Research studies test new ways to find and treat health problems. Some are looking for volunteers. Talk with your doctor before joining one.

Search ClinicalTrials.gov for studies on Viral gastroenteritis (stomach bug)