Norovirus Symptoms: What to Watch For and How Long They Last

You woke up fine, and a few hours later you can't stop running to the bathroom. The nausea hit out of nowhere, your stomach is cramping, and you're wondering whether it was something you ate, a bug going around, or something more serious. If symptoms came on fast and hard, there's a good chance you're dealing with norovirus, the most common cause of sudden vomiting and diarrhea in the US.

The good news: for most healthy people, norovirus is miserable but short-lived. Here's exactly what the symptoms look like, how long they usually last, and the warning signs that mean it's time to call a clinician.

What are the symptoms of norovirus?

Norovirus causes acute gastroenteritis, an inflammation of the stomach and intestines that people often call the 'stomach flu' (even though it has no biologic connection to influenza). The hallmark is a sudden, intense onset of stomach symptoms.

The core symptoms are:

• Nonbloody diarrhea (watery, not bloody)
• Vomiting
• Nausea
• Stomach or abdominal cramps
• Sometimes a low-grade fever, headache, and body aches

How long do norovirus symptoms last?

For most people, norovirus symptoms begin 12 to 48 hours after exposure to the virus and last about 1 to 3 days. The worst of it is often concentrated in a rough 24 to 48 hour stretch, after which people typically start to feel better and recover completely without any specific treatment.

Some people have a longer course. Prolonged illness lasting 4 to 6 days can occur, particularly in young children, older adults, and people who are hospitalized. It's also worth knowing that even after you feel well, you can keep spreading the virus. People shed large amounts of norovirus in stool and vomit, and shedding can continue for days to weeks after symptoms resolve, which is why hand hygiene matters even once you feel back to normal.

Does everyone get both vomiting and diarrhea?

No. While many people experience the full set of symptoms, some have only vomiting or only diarrhea. This is especially common in very young children. In one study, 35% of children under 2 had vomiting but not diarrhea.

So if you or your child has sudden, repeated vomiting with no diarrhea, that can still be norovirus. The pattern varies from person to person, which is part of why it's hard to diagnose by symptoms alone.

Norovirus vs. food poisoning vs. the flu

These often get confused because the symptoms overlap. A few distinctions can help:

• Food poisoning: Norovirus is actually the leading cause of foodborne illness in the US, responsible for about 58% of cases. So a lot of what people call 'food poisoning' is in fact norovirus spread through contaminated food, water, or surfaces.
• Influenza ('the flu'): Despite the nickname 'stomach flu,' norovirus has no biologic association with the flu virus. The flu is mainly a respiratory illness (fever, cough, body aches) rather than a vomiting-and-diarrhea illness.
• Other stomach bugs: Bloody diarrhea is not typical of norovirus. If you see blood, that points toward a different cause and is worth a call to a clinician.

How is norovirus treated?

There is currently no FDA-approved norovirus vaccine and no antiviral cure. Treatment is supportive, which mostly means staying hydrated and letting the illness run its course.

Practical steps while you recover:

• Sip fluids steadily; oral rehydration solutions help replace lost salts and water
• Rest, and reintroduce bland foods as your stomach settles
• Wash hands thoroughly with soap and water, especially after using the bathroom and before handling food
• Clean contaminated surfaces, since norovirus is extremely contagious and the infectious dose can be as low as 18 viral particles
• Avoid preparing food for others while sick and for a few days after you feel better

When should you see a doctor?

Most healthy adults ride out norovirus at home. The main danger is dehydration, and certain groups, young children, older adults, and people with other medical conditions, are at higher risk for severe dehydration that needs medical attention.

Seek medical care if you or someone you're caring for has signs of dehydration or a more serious course, such as:

• Little or no urination, very dry mouth and throat, or dizziness when standing
• In children: unusual sleepiness or fussiness, crying with few or no tears, or fewer wet diapers
• Inability to keep any fluids down for an extended period
• Bloody diarrhea, a high or persistent fever, or severe, unrelenting abdominal pain
• Symptoms that last longer than a few days or keep getting worse