Norovirus causes sudden-onset vomiting, diarrhea, nausea, and stomach pain, typically hitting 12 to 48 hours after exposure. It’s the leading cause of acute gastroenteritis in the United States, responsible for 19 to 21 million illnesses every year. Most people recover within one to two days, but the illness can be intense while it lasts.
The Main Symptoms
The hallmark of norovirus is the combination of vomiting and watery diarrhea, often occurring many times a day. Nausea and stomach pain round out the core symptoms. Some people also develop a low-grade fever, headache, and body aches, though these tend to take a back seat to the gastrointestinal misery.
The intensity can catch people off guard. Unlike a mild upset stomach, norovirus often leaves you feeling completely wiped out for 24 to 48 hours. The vomiting can be sudden and forceful, sometimes appearing before diarrhea starts. Not everyone gets both symptoms equally. Some people vomit repeatedly with little diarrhea, while others experience mostly diarrhea.
How Quickly Symptoms Appear
Symptoms typically show up 12 to 48 hours after you’re exposed to the virus. This incubation period is one of the distinguishing features of norovirus compared to other causes of food poisoning. Staph food poisoning, for example, hits much faster (within 30 minutes to 8 hours), while bacterial infections like Salmonella can take anywhere from 6 hours to 6 days, and Campylobacter may not cause symptoms for 2 to 5 days.
If you ate something questionable and started vomiting within an hour, norovirus is unlikely. If symptoms came on roughly a day later and involve both vomiting and diarrhea without blood, norovirus fits the pattern well. Bloody diarrhea is more characteristic of bacterial infections like Campylobacter, Salmonella, or certain strains of E. coli.
What the Virus Does Inside Your Body
Norovirus targets the lining of your small intestine. The gut is lined with a single layer of cells called enterocytes, and the virus may slip past these cells through specialized entry points that lack the protective mucus coating found elsewhere in the intestine. Once inside, the virus infects and replicates in immune cells deeper in the gut wall.
This immune response is what drives the symptoms. Your body essentially tries to flush the virus out, which is why diarrhea and vomiting are so prominent. The existing bacteria in your gut may also play a role: researchers have found that norovirus interacts with gut bacteria in ways that can enhance the infection and help the virus replicate more effectively.
How Long It Lasts
Most people feel significantly better within one to two days of symptoms starting. That’s a relatively short illness compared to many bacterial infections, but those 24 to 48 hours can be rough. The biggest concern during this window is dehydration from fluid loss through vomiting and diarrhea.
Even after you feel better, you’re still shedding the virus. This means you can spread norovirus to others for days after your symptoms resolve. Careful handwashing and avoiding food preparation for others during this period helps prevent passing the virus along.
Dehydration Warning Signs
Dehydration is the most common complication, and it’s the reason norovirus sends an estimated 465,000 people to emergency departments and causes roughly 109,000 hospitalizations in the U.S. each year. Adults aged 65 and older and young children face the highest risk. Norovirus causes an average of 900 deaths annually in the United States, mostly among older adults.
Watch for these signs that dehydration is becoming serious:
- Dry mouth and throat
- Decreased urine output or dark-colored urine
- Dizziness or lightheadedness when standing
- Unusual fatigue or listlessness
In children, dehydration can look different. A dehydrated child may cry with few or no tears, seem unusually sleepy, or become fussy and irritable. Infants and toddlers can dehydrate quickly because of their small body size, so staying on top of fluid intake is especially important.
Eating and Drinking During Recovery
The priority while you’re sick is replacing lost fluids. Small, frequent sips of water or an oral rehydration solution work better than trying to drink large amounts at once, which can trigger more vomiting. Once your appetite starts coming back, you can return to your normal diet. Fasting or following a restricted diet doesn’t speed recovery.
That said, a few things can make lingering diarrhea worse while your gut heals. Caffeinated drinks like coffee, tea, and some sodas can irritate the digestive tract. High-fat foods like fried items and fast food may be harder to tolerate. Sugary beverages and fruit juices can pull more water into the intestine and worsen diarrhea. Dairy products are worth approaching cautiously too, since some people have temporary difficulty digesting lactose for up to a month after a norovirus infection.
Preventing Spread at Home
Norovirus is extraordinarily contagious. It takes only a tiny amount of the virus to infect someone, and it can survive on surfaces for days. Regular cleaning products often aren’t enough. To properly disinfect contaminated surfaces, the CDC recommends a bleach solution of 5 to 25 tablespoons of standard household bleach per gallon of water, or an EPA-registered disinfectant specifically labeled as effective against norovirus.
Handwashing with soap and water is more effective than hand sanitizer against norovirus, because the virus lacks the outer lipid coating that alcohol-based sanitizers are designed to break down. If someone in your household is sick, cleaning bathrooms, door handles, and any surfaces they’ve touched with the bleach solution helps contain the spread.