Norovirus Symptoms, Causes & Treatment

Norovirus is one of the most common causes of viral gastroenteritis, often referred to as the winter vomiting bug. This condition is unpleasant and extremely contagious but typically resolves on its own after a few days.

What Is Viral (Norovirus) Infection?

If you ever heard of an entire cruise ship of people coming down with the same “stomach bug,” chances are that was norovirus. Fortunately, norovirus usually goes away on its own after a few days, but is pretty unpleasant and can spread extremely easily. The main symptoms are vomiting and diarrhea, which can be severe enough to require hydration with intravenous fluids. However, other treatments are rarely necessary. In the developing world where access to supportive care is less available, norovirus infection is still responsible for tens of thousands of deaths each year, primarily due to dehydration.

You can safely treat this condition at home. Make sure you drink plenty of water and fluids (Gatorade, Pediatlyte) to replace what is lost with diarrhea. If symptoms of dehydration occur or you are unable to keep down any liquids, seek care at your primary care physician or an urgent care.

Symptoms of Viral (Norovirus) Infection

Main symptoms

Once exposed, symptoms typically begin within 24 to 48 hours, often abruptly. Norovirus is best known for causing profound vomiting and diarrhea. As you would expect, these can occur with abdominal pain and basically anything on the spectrum of gastrointestinal discomfort (“GI upset”). Other common symptoms include the usual vague set of fever, malaise, and headache that are common to many kinds of viral infection.

All that vomiting and diarrhea, along with a loss of appetite, can cause significant dehydration. Since this is the most important complication of norovirus infection and the main way it can become dangerous, it is important to keep an eye out for symptoms of dehydration. These include:

  • Dizziness or lightheadedness: Particularly when standing (known as orthostasis)
  • Fainting
  • Dry mouth: This is often accompanied by significant thirst.
  • Decreased urination

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Causes of Viral (Norovirus) Infection

Norovirus gastroenteritis is caused by infection of the gastrointestinal (GI) tract with the pathogen (bug) known as norovirus, named for the town of Norwalk, Ohio where the first outbreak was identified. Like most norovirus outbreaks, it struck a single community during winter (though it can occur at any time) and it spread extremely rapidly. In a manner of days, half the students and teachers at an elementary school became infected. After severe vomiting and diarrhea, they recovered almost as quickly.

How does norovirus spread?

Norovirus infection is spread from person-to-person primarily via the fecal-oral route. This means that viral particles find their way from the digestive tract of an infected person into the digestive tract of a healthy person. There are a few ways this can happen, but classically it starts with an infected person who doesn’t wash their hands after using the bathroom. Alternatively, they may have vomited and not washed their hands, or even washed their hands properly but gotten microscopic particles on their clothing or nearby surfaces. Importantly, viral particles can also spread through food, drink, or bodies of water such as swimming pools.

How contagious is norovirus?

Norovirus is so contagious that even a tiny exposure can transmit the infection, requiring an initial number of less than 100 viral particles. That entire infectious dose (known as an “inoculum”) is only a tiny fraction of the width of a human hair. Meanwhile, an infected person sheds far more viral particles at a time.

However, the viral particles get from an infected person into the environment, they must then get into the digestive tract of a healthy person. This turns out to be surprisingly easy given how often we touch our faces and mouths without even realizing it. Consumption of contaminated food and drink is another particularly significant source of infection. Additionally, transmission can occur during activities such as smoking or swimming in pools which could expose a healthy person to infected body fluids.

Treatment Options and Prevention

Treatment of symptoms

Treatment of norovirus infection is supportive. This means that management focuses on supporting vital body functions and treating symptoms rather than attempting to cure the infection itself, which your body will do on its own. There are no effective antiviral agents for norovirus, while antibiotics will not help treat viral infection and can actually make things worse. The use of antidiarrheal agents is controversial; they often reduce symptoms but some evidence suggests they are more harmful than beneficial. Antiemetics (which treat vomiting) can be used for those who are unable to tolerate oral rehydration.

Methods of staying hydrated

Since dehydration is the most important complication of norovirus infection, the most important component of supportive treatment is ensuring adequate hydration. This can usually be achieved by ensuring plenty of fluid intake by mouth. Water helps, but oral electrolyte solutions such as Pedialyte are better absorbed and generally the most effective way to stay hydrated at home.

For those who become severely dehydrated, intravenous (IV) hydration may be needed to provide fluids directly into a vein. This level of dehydration can occur in anyone but is particularly common in those whose vomiting is so severe they are unable to tolerate oral fluids. Professional medical care is also particularly important for vulnerable populations such as the elderly, infants, and those with chronic or severe illnesses.


Since there is no cure for norovirus, prevention is the main defense. There is currently no vaccine to prevent norovirus, though efforts to develop one are underway. In the meantime, proper hand hygiene remains the mainstay of preventing norovirus infection. This means washing your hands regularly and thoroughly with soap and water. Hand sanitizer is not very effective at removing norovirus particles, so thorough hand washing is your best option. Times it is particularly important to wash your hands include:

  • Before eating or taking medications
  • Before preparing food or medications
  • After using the bathroom
  • After vomiting
  • After coming in contact with an infected person
  • After touching commonly used public surfaces (such as in an airport)

In addition to hand hygiene, other steps you can take to reduce the risk of contracting norovirus include:

  • Carefully wash uncooked foods: Such as fruits and vegetables before consumption
  • Avoid close contact with those who are unwell or recently infected
  • Don’t prepare food or medication when you’re sick: You should also keep sick individuals (including children or babies) away from food preparation areas.
  • Clean your living spaces: You should thoroughly clean and disinfect any surfaces potentially exposed to infected body fluids such as vomit or diarrhea.
  • Regularly wash your hands: Especially when in high-risk areas such as cruises or airports

Most people feel better within a day or two, but they can still spread disease (known as viral shedding) for days or even weeks later. This means that it’s particularly important to wash your hands regularly and thoroughly even after you start feeling better, and when possible, avoid preparing food or medications if you’ve been sick recently.

When to Seek Further Consultation

Since most cases of norovirus infection are self-limiting without significant risk, professional medical care is not always needed. Testing for norovirus is rare if ever necessary.

If you show signs of severe dehydration

Any signs of significant dehydration, particularly things like fainting or decreased urine output, are reasons to seek professional medical care promptly. This is perhaps the most important point of norovirus management since severe dehydration is an entirely preventable cause of organ damage and death.

If an elderly person or infant is ill

Additionally, certain groups such as the elderly, infants, and chronically ill persons are at particularly high risk of dehydration and other complications. These individuals would be well-served to receive professional medical care during any period of acute illness, including norovirus infection.

Questions Your Doctor May Ask to Diagnose

  • Any fever today or during the last week?
  • Are you sick enough to consider going to the emergency room right now?
  • Have you lost your appetite recently?
  • Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?
  • Have you experienced any nausea?

Self-diagnose with our free if you answer yes on any of these questions.

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