Stomach Bug Symptoms and How to Treat It

A stomach bug — viral gastroenteritis — causes watery diarrhea, cramping or pain in the abdomen, nausea and vomiting, and sometimes fever, according to the NIDDK. Symptoms tend to arrive within a day or two of exposure, hit hard, and fade within a few days. The whole treatment is replacing what you’re losing.

”Stomach flu” is neither the stomach nor the flu

The NIDDK puts it plainly: viral gastroenteritis is an infection of the intestines, not the stomach, and it is not caused by influenza viruses. The nickname is a genuine source of confusion in the U.S. — people assume a flu shot will prevent it, and it won’t. The flu vaccine protects against influenza, a respiratory virus that has nothing to do with norovirus.

If your illness is coughing and congestion rather than diarrhea, you’re in the other family entirely — see respiratory virus symptoms.

The symptoms, roughly in the order they arrive

• Nausea, usually the first sign that something is wrong
• Vomiting, often intense but short-lived, typically easing before the diarrhea does
• Watery diarrhea, without blood — blood in stool points away from a simple viral cause
• Abdominal cramping and pain
• Fever, sometimes; MedlinePlus adds chills, clammy skin or sweating, and muscle aches
• Headache and loss of appetite

Which virus you probably have

Four dominate. Norovirus is the most common cause in the United States, responsible for 19 to 21 million cases a year per the NIDDK. Rotavirus is the classic cause in young children, though far less common since routine infant vaccination. Adenovirus and astrovirus fill out the list, and each runs on its own clock — see how long does a stomach bug last.

Transmission is fecal-oral: contaminated hands, surfaces, food or water. Norovirus in particular survives on surfaces and takes very few viral particles to infect, which is why it tears through cruise ships, schools and nursing homes.

Rehydration is the treatment, and the details matter

There is no antiviral for this. What you do is keep up with fluid losses while the infection runs its course. The NIDDK’s guidance:

1. Drink plenty of liquids — water, juice, sports drinks and broths for adults, plus salty foods like saltine crackers to help replace electrolytes.
2. Use an oral rehydration solution for children — Pedialyte, Naturalyte, Infalyte or CeraLyte, as directed. These are formulated for the salt-to-sugar ratio the gut absorbs best; sports drinks are not a substitute for a sick child.
3. Keep infants on breast milk or formula as usual, and ask a doctor before giving an oral rehydration solution to an infant.
4. Eat normally once your appetite returns. Some people do better temporarily limiting caffeine, high-fat foods, very sugary drinks and dairy, since lactose intolerance can be temporary after gastroenteritis.

When it stops being a home problem

Get medical care for diarrhea lasting more than several days, blood in the stool, no urine for 8 hours or more, confusion, dizziness, or vomiting that keeps any liquid down. Infants, young children, older adults and people with weakened immune systems have less margin — the NIDDK names them as the groups most likely to have severe symptoms. For the infant version of this picture, see stomach bug in babies, and for the wider view, viral infection symptoms.

This content is informational and does not replace medical evaluation, diagnosis, or treatment.