Last reviewed: October 26, 2026 · Based on guidance from the American Academy of Pediatrics and the latest UK Health Security Agency norovirus surveillance.
Quick answer: A stomach bug in babies, usually norovirus or rotavirus, causes sudden vomiting and watery diarrhea, sometimes with a mild fever. Most babies recover in 2–3 days, a little longer for younger infants. The real danger is dehydration, so keep offering breast milk or formula in small, frequent amounts, and ask your pediatrician about an oral rehydration solution like Pedialyte; the label says to check with a doctor before using it in babies under 1 year. Call your pediatrician right away if your baby has fewer wet diapers, no tears, a sunken soft spot, green or bloody vomit, or seems unusually sleepy.
Stomach bug season is here. Norovirus, the “winter vomiting bug”, circulates most from late autumn through spring, and young children are hit hardest. In the UK, health officials reported that norovirus lab reports for the 2026–27 season so far were 33% higher than the five-season average by early October, with the highest rates in children aged 0 to 4, according to the UK Health Security Agency. In the US, around 460,000 people, mostly young children, go to the emergency department with norovirus every year, according to the American Academy of Pediatrics.
This guide covers what a stomach bug looks like in a baby, the signs of dehydration to watch for, how to rehydrate safely, whether Pedialyte is OK for babies, and exactly when to call the doctor.
Stomach Bug Symptoms in Babies
A stomach bug (viral gastroenteritis) usually comes on suddenly. Common symptoms include:
- Vomiting, often several times in the first hours
- Watery diarrhea, sometimes frequent and explosive
- Fussiness, crying, or pulling legs up from tummy cramps
- Not wanting to feed, or vomiting soon after feeds
- Low fever
- Being more tired or sleepy than usual
Vomiting tends to settle within the first day, while diarrhea can last a few days longer. Changes in stool are normal during and after a stomach bug; our baby poop color guide explains which colors are fine and which need a call to your doctor.
Vomiting or Just Spit-Up?
Spit-up is an effortless dribble of milk after feeds, and the baby is otherwise happy. Vomiting is forceful, often larger in volume, and the baby looks unwell. If your baby spits up a lot but is feeding and gaining weight, read our guide to reflux in infants. Forceful, projectile vomiting after every feed in a baby a few weeks old needs a same-day call to your pediatrician.
Signs of Dehydration in Babies
Babies lose fluid much faster than adults, so dehydration can develop within hours when they’re vomiting and having diarrhea. Check these signs regularly:
Well hydrated | Getting dehydrated: call your pediatrician | Seriously dehydrated: go to the ER |
Regular wet diapers | Fewer wet diapers than usual, dark yellow urine | No wet diaper for 8 hours or more |
Moist mouth and tongue | Dry, sticky mouth | Very dry mouth, cracked lips |
Tears when crying | Fewer tears | No tears at all |
Alert and interested | Unusually fussy or sleepy | Very sleepy, floppy, or hard to wake |
Soft spot is flat | Soft spot slightly sunken | Sunken soft spot and eyes; cool, blotchy hands and feet |
A useful rule from Children’s Hospital of The King’s Daughters: fewer than six wet diapers a day in an infant is a reason to call your pediatrician.
How to Rehydrate a Baby With a Stomach Bug
The goal is to replace lost fluids slowly and steadily. Big gulps often come straight back up; tiny sips usually stay down.
- Keep breastfeeding or bottle-feeding. Breast milk and formula are still your baby’s best fluids. Offer shorter, more frequent feeds rather than full ones.
- Go small and often. If your baby keeps vomiting, offer about 1 teaspoon (5 mL) every 1–2 minutes with a spoon, syringe or medicine dropper, as pediatricians at Children’s Hospital of The King’s Daughters recommend.
- Pause after vomiting. If your baby vomits, wait about 30 minutes, then start again with small sips.
- Increase slowly. Once small amounts stay down for an hour or two, gradually offer more.
- Ask about an oral rehydration solution. If milk or formula isn’t staying down, your pediatrician may suggest an electrolyte solution made for babies. Don’t make your own at home, and avoid plain water as the main drink, which doesn’t replace lost salts.
- Skip juice, soda and sports drinks. They’re too high in sugar and too low in salts, and can make diarrhea worse.
Pedialyte for Babies: Is It Safe?
Oral rehydration solutions such as Pedialyte, Enfalyte and similar store brands are designed to replace water and electrolytes in the right balance, which is why pediatricians often recommend them for vomiting and diarrhea. But for babies, check first:
- Under 1 year: the Pedialyte label says to consult your doctor before using it in infants under 1 year, because babies dehydrate faster and need individual advice.
- Powder packs and freezer pops are not for children under 1 year.
- Don’t dilute it or mix it with milk, formula or juice. That changes the balance of salts and sugar.
- Use it alongside breast milk or formula, not as a long-term replacement. Your pediatrician will tell you how much to offer for your baby’s age and weight.
When to Call the Doctor or Go to the ER
Go to the ER or call 911 if your baby:
- Has no wet diaper for 8 hours or more
- Is very sleepy, floppy, or hard to wake
- Has a sunken soft spot or sunken eyes, or cries without tears
- Has green (bile-colored) vomit, or blood in vomit or stool
- Has a swollen, hard or very painful tummy
Call your pediatrician the same day if your baby:
- Is under 6 months old and vomiting or has diarrhea
- Is under 3 months old and has a fever of 100.4°F (38°C) or higher
- Can’t keep any fluids down for several hours, or vomits more than a few times in 24 hours
- Refuses to feed or to take oral rehydration solution
- Has diarrhea lasting more than a few days
- Has a chronic health condition or weakened immune system
If your baby has a fever with the stomach bug, see our tips on how to dress a baby with a fever at night. And if your baby has a cough and breathing symptoms too, it may be flu; read our guide to flu in babies.
How Long Does a Stomach Bug Last in Babies, and How Contagious Is It?
Most children recover from norovirus in 2–3 days, though younger babies can take a little longer. The virus is extremely contagious: it can spread before symptoms start and for at least 48 hours after they stop, according to the AAP. Babies should stay home from daycare until vomiting and diarrhea have been gone for at least 48 hours and stools are contained in the diaper.
To stop it spreading through your home:
- Wash hands with soap and warm water for at least 20 seconds. Hand sanitizer doesn’t kill norovirus.
- Clean surfaces with a bleach solution of about 5–25 tablespoons of household bleach per gallon of water, left on for 5 minutes, or use an EPA-registered disinfectant that works against norovirus.
- Wash soiled clothes and bedding in hot water on the longest cycle, and dry on high heat.
- Change diapers in one spot, bag them, and clean the changing area after each change.
- Keep the sick baby away from newborns and vulnerable relatives where you can.
What to Feed a Baby After a Stomach Bug
Once fluids are staying down, babies who eat solids can go back to their usual foods in small amounts. A few little bites at a time are less likely to trigger more vomiting. There’s no need for a strict bland diet, but offer easy foods your baby already likes, and keep up breast milk or formula throughout. If you’re unsure how much your baby should be taking, our guide to how often a newborn eats can help you spot when intake is low.
The rotavirus vaccine, given by mouth in the first months of life, protects babies against rotavirus, another common cause of severe vomiting and diarrhea. There’s no vaccine for norovirus yet, so handwashing is your best defense.
Frequently Asked Questions About Stomach Bugs in Babies
How long does a stomach bug last in babies?
Most babies recover from norovirus in 2–3 days, sometimes a little longer in young infants. Vomiting usually eases first; diarrhea can last a few more days.
Can I give Pedialyte to my baby?
Ask your pediatrician first if your baby is under 1 year; the label says to consult a doctor for infants. For older babies, it’s a good way to replace fluids and salts in small, frequent sips.
What are the signs of dehydration in a baby?
Fewer wet diapers (or none for 8 hours), a dry mouth, no tears when crying, a sunken soft spot, and being unusually sleepy or fussy. Call your pediatrician at the first signs.
Should I keep breastfeeding if my baby has a stomach bug?
Yes. Keep breastfeeding or bottle-feeding, offering shorter and more frequent feeds. Breast milk and formula are still the best fluids for babies.
When should I worry about my baby throwing up?
Get help urgently for green or bloody vomit, a swollen tummy, signs of dehydration, or a baby who is hard to wake. Call the same day if your baby is under 6 months or can’t keep any fluids down.
How long is norovirus contagious in babies?
From before symptoms start until at least 48 hours after they stop. Keep your baby home from daycare until vomiting and diarrhea have been gone for 48 hours.
The Bottom Line
Most babies get over a stomach bug in a few days. Your job is to keep fluids going: small, frequent breast milk or formula feeds, and an oral rehydration solution if your pediatrician recommends one. Watch wet diapers, tears and alertness closely, and get help quickly for any signs of dehydration, green or bloody vomit, or a baby who is hard to wake. Thorough handwashing with soap is the best way to stop norovirus spreading through the family.
This article is for general information and isn’t a substitute for medical advice. Always contact your pediatrician with questions about your baby’s health. In an emergency, call 911.
