Norovirus causes sudden, intense vomiting and watery diarrhea that typically hit within 12 to 48 hours of exposure. Most people recover fully in one to three days, but the illness can feel severe while it lasts. Here’s what to expect from start to finish.
The Main Symptoms
The hallmark of norovirus is the rapid onset of nausea, vomiting, and diarrhea. Vomiting often comes first and can be forceful and frequent, sometimes striking without much warning. Diarrhea is watery rather than bloody, and many people experience both symptoms simultaneously for the first 24 hours.
Beyond the gut, norovirus commonly triggers fever (usually low-grade), headache, body aches, and stomach cramps. These symptoms tend to overlap with the vomiting and diarrhea rather than appearing before them. Some people describe a general feeling of exhaustion and chills that makes it hard to get out of bed, even between bouts of vomiting.
Why It Hits So Fast and Hard
Norovirus works differently from many stomach infections. The virus blunts the tiny finger-like projections lining the small intestine, which are responsible for absorbing nutrients and water. This damage disrupts fat and sugar absorption and causes the intestinal lining to leak fluid, producing the watery diarrhea. The vomiting, interestingly, isn’t caused by visible damage to the stomach at all. Instead, the virus changes how the stomach contracts and empties, essentially slowing normal movement and triggering the vomiting reflex from above.
This combination of impaired absorption in the intestine and disrupted stomach emptying is why the illness feels so relentless. Your body is simultaneously unable to absorb what’s already inside and actively pushing everything out from both directions. It only takes a tiny number of viral particles to start this process, which is why norovirus spreads so efficiently through households, cruise ships, and schools.
Timeline From Exposure to Recovery
The clock starts ticking the moment you’re exposed. Here’s the general progression:
- Hours 12 to 48 (incubation): No symptoms yet, though you may already be shedding virus. Some people feel mildly “off” toward the end of this window.
- Day 1: Sudden onset of nausea and vomiting, often followed by diarrhea within hours. This is typically the worst day. Fever, headache, and body aches peak here.
- Days 2 to 3: Vomiting usually tapers off first. Diarrhea may linger a bit longer. Energy starts returning, though appetite is often still low.
- Days 4 to 7: Most people feel noticeably better but may still have loose stools or mild fatigue.
The illness is self-limited, meaning it resolves on its own without medication. There’s no antiviral treatment for norovirus. Recovery is really about staying hydrated while your body clears the infection.
Dehydration: The Real Danger
The symptoms themselves are miserable but temporary. The actual medical risk is dehydration from the combined fluid loss of vomiting and diarrhea. Young children, older adults, and people with weakened immune systems are most vulnerable because they have less margin for fluid loss and may not be able to drink enough to keep up.
Signs that dehydration is becoming a problem include dry mouth, dark yellow urine or very little urine output, dizziness when standing, and in children, crying without tears or unusual sleepiness. If you can keep sipping small amounts of fluid, even just a few tablespoons every 10 to 15 minutes, that’s often enough to prevent serious dehydration. Oral rehydration solutions work better than plain water because they replace the salts your body is losing.
How It Differs From Food Poisoning
Norovirus is often called “food poisoning” or “stomach flu,” but it behaves differently from bacterial infections like those caused by Salmonella or E. coli. Bacterial food poisoning more commonly causes bloody or mucus-filled diarrhea, higher fevers, and can last a week or more. Norovirus diarrhea is watery, fevers stay low, and the whole illness wraps up faster. The vomiting with norovirus also tends to be more prominent than with most bacterial infections, where diarrhea is the dominant symptom.
Rotavirus, which causes similar symptoms, primarily affects young children and is now much less common thanks to routine vaccination. In adults, norovirus is the leading cause of acute gastroenteritis.
You’re Still Contagious After Feeling Better
One of the trickiest things about norovirus is the gap between feeling recovered and actually being done shedding the virus. You can continue releasing virus in your stool for up to two weeks after your symptoms resolve. For people with underlying health conditions, shedding can persist for several weeks to several months.
This matters most for hand hygiene. Even when you feel completely fine, thorough handwashing with soap and water (not just hand sanitizer, which is less effective against norovirus) remains important. If you work in food service or healthcare, most guidelines recommend staying out for at least 48 hours after your last episode of vomiting or diarrhea.
A Shifting Virus
Norovirus isn’t a single virus but a family of related strains that shift over time, similar to how flu strains rotate. For years, one genotype (GII.4) dominated outbreaks in the United States. Starting in 2024, a different strain called GII.17 overtook it, accounting for more than 50% of all outbreaks each month from May 2024 through March 2025. This shift doesn’t appear to change the core symptoms, but it may explain why some people who’ve had norovirus before get hit again. Prior infection with one strain doesn’t fully protect you against a different one, which is why repeat infections throughout life are common.