Most stomach bugs in kids last between 1 and 3 days for the worst symptoms, though diarrhea can linger for up to a week or longer depending on the virus. The illness tends to follow a predictable pattern: vomiting hits first and hard, then tapers off within a day, while loose stools take over and gradually improve over the next several days.
The Typical Timeline From Start to Finish
A stomach bug usually begins 12 to 48 hours after your child is exposed to the virus. The first sign is almost always vomiting, which can be intense for the first 3 to 4 hours. During this early phase, your child may throw up everything, including small sips of water. Watery diarrhea typically follows within 12 to 24 hours of the vomiting starting.
Vomiting rarely lasts beyond 24 hours. If your child is still vomiting after a full day, that’s worth a call to their pediatrician. Diarrhea is the more stubborn symptom. For rotavirus, one of the most common causes in young children, vomiting and watery diarrhea last 3 to 8 days total. Norovirus, the other major culprit, tends to wrap up faster, usually within 1 to 3 days. Low-grade fever and stomach cramps often accompany both but usually resolve alongside the vomiting.
Here’s a rough day-by-day picture for a typical case:
- Day 1: Vomiting begins suddenly, often with fever and cramping. Diarrhea may start by evening.
- Days 2 to 3: Vomiting stops or becomes infrequent. Diarrhea continues, sometimes 4 to 6 loose stools a day. Energy is low.
- Days 4 to 7: Stools gradually firm up. Appetite slowly returns. Your child starts acting more like themselves.
Some kids bounce back in 48 hours. Others, especially toddlers with rotavirus, can have watery stools for a full week or slightly longer. Both scenarios are normal as long as your child stays hydrated.
How Long Kids Stay Contagious
Your child is most contagious during the first few days of illness and for a short window after symptoms stop. Research on caliciviruses (the family that includes norovirus) found that 95% of stool samples collected within four days of symptom onset contained the virus. By days 5 through 9, that dropped to about 50%. After that, the virus was rarely detected.
In practical terms, this means your child can still spread the bug for several days after they feel better. The CDC’s school guidance says children can return once vomiting has resolved overnight and they can hold down food and liquids in the morning. For diarrhea, the standard is that episodes have improved to no more than two above your child’s normal number of bowel movements in a 24-hour period. Thorough hand washing, especially after bathroom trips, is the single most effective way to stop it from tearing through the rest of the household.
Keeping Your Child Hydrated
Dehydration is the main risk with any stomach bug in kids, not the virus itself. The combination of vomiting and diarrhea can drain fluids fast, especially in babies and toddlers.
The key strategy is small, frequent sips rather than large gulps. Start with about 5 milliliters (one teaspoon) of an oral rehydration solution every 5 minutes, then gradually increase as your child tolerates it. Trying to give a big cup of water or juice to a vomiting child almost always backfires. For mild dehydration, the general target is roughly 50 milliliters per kilogram of your child’s body weight over 4 hours. So a 10-kilogram toddler (about 22 pounds) would need around 500 milliliters, or about 2 cups, spread across those 4 hours in tiny amounts. After each watery stool, an extra small cup (up to 240 milliliters) helps replace what was lost.
For breastfed infants, keep nursing as often as your baby will take it. Formula-fed babies should continue their regular formula. Neither needs to be diluted or switched unless your pediatrician says otherwise.
What to Feed During and After
The old advice to stick with bananas, rice, applesauce, and toast (the BRAT diet) has fallen out of favor. Research shows that following a restricted diet does not help treat viral gastroenteritis, and most experts no longer recommend it. A limited diet can actually slow recovery by depriving your child of the calories and nutrients they need to heal.
The current recommendation is simple: once your child’s appetite returns, offer their normal foods. You don’t need to wait for diarrhea to fully resolve before reintroducing regular meals. Start with whatever sounds appealing to them, whether that’s pasta, chicken, crackers, or fruit. Avoid sugary drinks like apple juice and soda, which can make diarrhea worse. Water and oral rehydration solutions are better choices until things settle down.
Signs That Need Medical Attention
Most stomach bugs resolve on their own, but dehydration can escalate quickly in small children. Watch for these warning signs:
- Fewer wet diapers than usual (or significantly less urine in older kids)
- No tears when crying
- A sunken soft spot on a baby’s head
- Sunken eyes or unusual drowsiness
- Dry mouth or lips
Beyond dehydration, certain symptoms point to something more serious. Persistent vomiting that doesn’t improve even with small, slow sips of rehydration fluid needs evaluation. So does a high fever lasting several days, blood in the diarrhea or vomit, or severe abdominal pain that goes beyond typical cramping. Children under 6 months and kids with chronic health conditions should be seen by a doctor whenever they get a stomach bug, even if symptoms seem mild, because they have less margin for fluid loss.